diff --git a/packages/stream_chat/lib/src/api/channel.dart b/packages/stream_chat/lib/src/api/channel.dart
index 35989a72..17755b6d 100644
--- a/packages/stream_chat/lib/src/api/channel.dart
+++ b/packages/stream_chat/lib/src/api/channel.dart
@@ -204,7 +204,8 @@ class Channel {
   /// Channel extra data as a stream
   Stream<Map<String, dynamic>> get extraDataStream {
     _checkInitialized();
-    return state!.channelStateStream.map(
+    return state!.channelStateStream
+        .map(
       (cs) => cs.channel?.extraData ?? _extraData,
     );
   }
diff --git a/packages/stream_chat_flutter/lib/src/attachment/attachment_title.dart b/packages/stream_chat_flutter/lib/src/attachment/attachment_title.dart
index 0ad06cc0..e2686638 100644
--- a/packages/stream_chat_flutter/lib/src/attachment/attachment_title.dart
+++ b/packages/stream_chat_flutter/lib/src/attachment/attachment_title.dart
@@ -11,7 +11,7 @@ class AttachmentTitle extends StatelessWidget {
     required this.messageTheme,
   }) : super(key: key);
 
-  final MessageTheme? messageTheme;
+  final MessageTheme messageTheme;
   final Attachment attachment;
 
   @override
@@ -32,7 +32,7 @@ class AttachmentTitle extends StatelessWidget {
               Text(
                 attachment.title!,
                 overflow: TextOverflow.ellipsis,
-                style: messageTheme?.messageText?.copyWith(
+                style: messageTheme.messageText?.copyWith(
                   color: StreamChatTheme.of(context).colorTheme.accentBlue,
                   fontWeight: FontWeight.bold,
                 ),
@@ -47,7 +47,7 @@ class AttachmentTitle extends StatelessWidget {
                     .toList()
                     .reversed
                     .join('.'),
-                style: messageTheme?.messageText,
+                style: messageTheme.messageText,
               ),
           ],
         ),
diff --git a/packages/stream_chat_flutter/lib/src/attachment/file_attachment.dart b/packages/stream_chat_flutter/lib/src/attachment/file_attachment.dart
index 929cddc2..90ef92b1 100644
--- a/packages/stream_chat_flutter/lib/src/attachment/file_attachment.dart
+++ b/packages/stream_chat_flutter/lib/src/attachment/file_attachment.dart
@@ -155,7 +155,7 @@ class FileAttachment extends AttachmentWidget {
         shape: _getDefaultShape(context),
         child: source.when(
           local: () => VideoThumbnailImage(
-            video: attachment.file?.path,
+            video: attachment.file!.path!,
             placeholderBuilder: (_) {
               return Center(
                 child: Container(
@@ -167,7 +167,7 @@ class FileAttachment extends AttachmentWidget {
             },
           ),
           network: () => VideoThumbnailImage(
-            video: attachment.assetUrl,
+            video: attachment.assetUrl!,
             placeholderBuilder: (_) {
               return Center(
                 child: Container(
diff --git a/packages/stream_chat_flutter/lib/src/attachment/image_attachment.dart b/packages/stream_chat_flutter/lib/src/attachment/image_attachment.dart
index 6ac48f59..1ff9b8a9 100644
--- a/packages/stream_chat_flutter/lib/src/attachment/image_attachment.dart
+++ b/packages/stream_chat_flutter/lib/src/attachment/image_attachment.dart
@@ -10,7 +10,7 @@ import 'attachment_title.dart';
 import 'attachment_widget.dart';
 
 class ImageAttachment extends AttachmentWidget {
-  final MessageTheme? messageTheme;
+  final MessageTheme messageTheme;
   final bool showTitle;
   final ShowMessageCallback? onShowMessage;
   final ValueChanged<ReturnActionType>? onReturnAction;
@@ -20,8 +20,8 @@ class ImageAttachment extends AttachmentWidget {
     Key? key,
     required Message message,
     required Attachment attachment,
+    required this.messageTheme,
     Size? size,
-    this.messageTheme,
     this.showTitle = false,
     this.onShowMessage,
     this.onReturnAction,
@@ -157,7 +157,7 @@ class ImageAttachment extends AttachmentWidget {
           ),
           if (showTitle && attachment.title != null)
             Material(
-              color: messageTheme?.messageBackgroundColor,
+              color: messageTheme.messageBackgroundColor,
               child: AttachmentTitle(
                 messageTheme: messageTheme,
                 attachment: attachment,
diff --git a/packages/stream_chat_flutter/lib/src/attachment/video_attachment.dart b/packages/stream_chat_flutter/lib/src/attachment/video_attachment.dart
index 05c511b5..4ffbee1b 100644
--- a/packages/stream_chat_flutter/lib/src/attachment/video_attachment.dart
+++ b/packages/stream_chat_flutter/lib/src/attachment/video_attachment.dart
@@ -8,7 +8,7 @@ import 'attachment_upload_state_builder.dart';
 import 'attachment_widget.dart';
 
 class VideoAttachment extends AttachmentWidget {
-  final MessageTheme? messageTheme;
+  final MessageTheme messageTheme;
   final ShowMessageCallback? onShowMessage;
   final ValueChanged<ReturnActionType>? onReturnAction;
   final VoidCallback? onAttachmentTap;
@@ -17,8 +17,8 @@ class VideoAttachment extends AttachmentWidget {
     Key? key,
     required Message message,
     required Attachment attachment,
+    required this.messageTheme,
     Size? size,
-    this.messageTheme,
     this.onShowMessage,
     this.onReturnAction,
     this.onAttachmentTap,
@@ -39,7 +39,7 @@ class VideoAttachment extends AttachmentWidget {
         return _buildVideoAttachment(
           context,
           VideoThumbnailImage(
-            video: attachment.file?.path,
+            video: attachment.file!.path!,
             height: size?.height,
             width: size?.width,
             fit: BoxFit.cover,
@@ -54,7 +54,7 @@ class VideoAttachment extends AttachmentWidget {
         return _buildVideoAttachment(
           context,
           VideoThumbnailImage(
-            video: attachment.assetUrl,
+            video: attachment.assetUrl!,
             height: size?.height,
             width: size?.width,
             fit: BoxFit.cover,
@@ -116,7 +116,7 @@ class VideoAttachment extends AttachmentWidget {
           ),
           if (attachment.title != null)
             Material(
-              color: messageTheme?.messageBackgroundColor,
+              color: messageTheme.messageBackgroundColor,
               child: AttachmentTitle(
                 messageTheme: messageTheme,
                 attachment: attachment,
diff --git a/packages/stream_chat_flutter/lib/src/deleted_message.dart b/packages/stream_chat_flutter/lib/src/deleted_message.dart
index c0387982..b3071904 100644
--- a/packages/stream_chat_flutter/lib/src/deleted_message.dart
+++ b/packages/stream_chat_flutter/lib/src/deleted_message.dart
@@ -14,7 +14,7 @@ class DeletedMessage extends StatelessWidget {
   }) : super(key: key);
 
   /// The theme of the message
-  final MessageTheme? messageTheme;
+  final MessageTheme messageTheme;
 
   /// The border radius of the message text
   final BorderRadiusGeometry? borderRadiusGeometry;
@@ -34,7 +34,7 @@ class DeletedMessage extends StatelessWidget {
       transform: Matrix4.rotationY(reverse ? pi : 0),
       alignment: Alignment.center,
       child: Material(
-        color: messageTheme?.messageBackgroundColor,
+        color: messageTheme.messageBackgroundColor,
         shape: shape ??
             RoundedRectangleBorder(
               borderRadius: borderRadiusGeometry ?? BorderRadius.zero,
@@ -61,9 +61,9 @@ class DeletedMessage extends StatelessWidget {
             alignment: Alignment.center,
             child: Text(
               'Message deleted',
-              style: messageTheme?.messageText?.copyWith(
+              style: messageTheme.messageText?.copyWith(
                 fontStyle: FontStyle.italic,
-                color: messageTheme?.createdAt?.color,
+                color: messageTheme.createdAt?.color,
               ),
             ),
           ),
diff --git a/packages/stream_chat_flutter/lib/src/full_screen_media.dart b/packages/stream_chat_flutter/lib/src/full_screen_media.dart
index 4956fb28..f960b5ee 100644
--- a/packages/stream_chat_flutter/lib/src/full_screen_media.dart
+++ b/packages/stream_chat_flutter/lib/src/full_screen_media.dart
@@ -177,7 +177,6 @@ class _FullScreenMediaState extends State<FullScreenMedia>
                     Navigator.of(context).pop();
                   },
                   message: widget.message,
-                  urls: widget.mediaAttachments,
                   currentIndex: _currentPage,
                   onShowMessage: () {
                     widget.onShowMessage?.call(
diff --git a/packages/stream_chat_flutter/lib/src/image_footer.dart b/packages/stream_chat_flutter/lib/src/image_footer.dart
index a25d1be3..27c92674 100644
--- a/packages/stream_chat_flutter/lib/src/image_footer.dart
+++ b/packages/stream_chat_flutter/lib/src/image_footer.dart
@@ -221,8 +221,8 @@ class _ImageFooterState extends State<ImageFooter> {
                             child: FittedBox(
                               fit: BoxFit.cover,
                               child: VideoThumbnailImage(
-                                video: attachment.file?.path ??
-                                    attachment.assetUrl,
+                                video: (attachment.file?.path ??
+                                    attachment.assetUrl)!,
                               ),
                             ),
                           );
diff --git a/packages/stream_chat_flutter/lib/src/image_group.dart b/packages/stream_chat_flutter/lib/src/image_group.dart
index 85e28497..a08d13de 100644
--- a/packages/stream_chat_flutter/lib/src/image_group.dart
+++ b/packages/stream_chat_flutter/lib/src/image_group.dart
@@ -15,7 +15,7 @@ class ImageGroup extends StatelessWidget {
 
   final List<Attachment> images;
   final Message message;
-  final MessageTheme? messageTheme;
+  final MessageTheme messageTheme;
   final Size size;
   final ShowMessageCallback? onShowMessage;
 
diff --git a/packages/stream_chat_flutter/lib/src/image_header.dart b/packages/stream_chat_flutter/lib/src/image_header.dart
index 1cec9c36..6837722c 100644
--- a/packages/stream_chat_flutter/lib/src/image_header.dart
+++ b/packages/stream_chat_flutter/lib/src/image_header.dart
@@ -27,15 +27,13 @@ class ImageHeader extends StatelessWidget implements PreferredSizeWidget {
   final String userName;
   final String sentAt;
 
-  final List<Attachment> urls;
-  final currentIndex;
+  final int currentIndex;
 
   /// Creates a channel header
   ImageHeader({
     Key? key,
     required this.message,
-    this.urls = const [],
-    this.currentIndex,
+    this.currentIndex = 0,
     this.showBackButton = true,
     this.onBackPressed,
     this.onShowMessage,
diff --git a/packages/stream_chat_flutter/lib/src/message_actions_modal.dart b/packages/stream_chat_flutter/lib/src/message_actions_modal.dart
index 5d97bdf6..b737bd09 100644
--- a/packages/stream_chat_flutter/lib/src/message_actions_modal.dart
+++ b/packages/stream_chat_flutter/lib/src/message_actions_modal.dart
@@ -20,7 +20,7 @@ class MessageActionsModal extends StatefulWidget {
   final OnMessageTap? onThreadReplyTap;
   final OnMessageTap? onReplyTap;
   final Message message;
-  final MessageTheme? messageTheme;
+  final MessageTheme messageTheme;
   final bool showReactions;
   final OnMessageTap? onCopyTap;
   final bool showDeleteMessage;
@@ -92,7 +92,7 @@ class _MessageActionsModalState extends State<MessageActionsModal> {
       }
     }
     final roughSentenceSize = messageTextLength *
-        (widget.messageTheme?.messageText?.fontSize ?? 1) *
+        (widget.messageTheme.messageText?.fontSize ?? 1) *
         1.2;
     final divFactor = widget.message.attachments.isNotEmpty == true
         ? 1
@@ -149,7 +149,6 @@ class _MessageActionsModalState extends State<MessageActionsModal> {
                                     0.0),
                                 child: ReactionPicker(
                                   message: widget.message,
-                                  messageTheme: widget.messageTheme,
                                 ),
                               ),
                             SizedBox(height: 8),
diff --git a/packages/stream_chat_flutter/lib/src/message_input.dart b/packages/stream_chat_flutter/lib/src/message_input.dart
index c7ddb5f1..33917de0 100644
--- a/packages/stream_chat_flutter/lib/src/message_input.dart
+++ b/packages/stream_chat_flutter/lib/src/message_input.dart
@@ -1661,7 +1661,7 @@ class MessageInputState extends State<MessageInput> {
             VideoThumbnailImage(
               height: 104,
               width: 104,
-              video: attachment.file?.path ?? attachment.assetUrl,
+              video: (attachment.file?.path ?? attachment.assetUrl)!,
               fit: BoxFit.cover,
             ),
             Positioned(
diff --git a/packages/stream_chat_flutter/lib/src/message_list_view.dart b/packages/stream_chat_flutter/lib/src/message_list_view.dart
index f444224d..8f36baeb 100644
--- a/packages/stream_chat_flutter/lib/src/message_list_view.dart
+++ b/packages/stream_chat_flutter/lib/src/message_list_view.dart
@@ -832,7 +832,7 @@ class _MessageListViewState extends State<MessageListView> {
             break;
           case ReturnActionType.reply:
             FocusScope.of(context).unfocus();
-            widget.onMessageSwiped!(message);
+            widget.onMessageSwiped?.call(message);
             break;
         }
       },
@@ -1008,7 +1008,7 @@ class _MessageListViewState extends State<MessageListView> {
             break;
           case ReturnActionType.reply:
             FocusScope.of(context).unfocus();
-            widget.onMessageSwiped!(message);
+            widget.onMessageSwiped?.call(message);
             break;
         }
       },
@@ -1034,7 +1034,7 @@ class _MessageListViewState extends State<MessageListView> {
         child: Swipeable(
           onSwipeEnd: () {
             FocusScope.of(context).unfocus();
-            widget.onMessageSwiped!(message);
+            widget.onMessageSwiped?.call(message);
           },
           backgroundIcon: StreamSvgIcon.reply(
             color: StreamChatTheme.of(context).colorTheme.accentBlue,
diff --git a/packages/stream_chat_flutter/lib/src/message_reactions_modal.dart b/packages/stream_chat_flutter/lib/src/message_reactions_modal.dart
index ed9534ac..9fa35cb6 100644
--- a/packages/stream_chat_flutter/lib/src/message_reactions_modal.dart
+++ b/packages/stream_chat_flutter/lib/src/message_reactions_modal.dart
@@ -14,7 +14,7 @@ import 'stream_chat_theme.dart';
 
 class MessageReactionsModal extends StatelessWidget {
   final Message message;
-  final MessageTheme? messageTheme;
+  final MessageTheme messageTheme;
   final bool reverse;
   final bool showReactions;
   final DisplayWidget showUserAvatar;
@@ -53,7 +53,7 @@ class MessageReactionsModal extends StatelessWidget {
       }
     }
     final roughSentenceSize =
-        messageTextLength * (messageTheme?.messageText?.fontSize ?? 1) * 1.2;
+        messageTextLength * (messageTheme.messageText?.fontSize ?? 1) * 1.2;
     final divFactor = message.attachments.isNotEmpty == true
         ? 1
         : (roughSentenceSize == 0 ? 1 : (roughSentenceSize / roughMaxSize));
@@ -105,7 +105,6 @@ class MessageReactionsModal extends StatelessWidget {
                                   0.0),
                               child: ReactionPicker(
                                 message: message,
-                                messageTheme: messageTheme,
                               ),
                             ),
                           const SizedBox(height: 8),
@@ -244,9 +243,9 @@ class MessageReactionsModal extends StatelessWidget {
                   child: ReactionBubble(
                     reactions: [reaction],
                     flipTail: !reverse,
-                    borderColor: messageTheme?.reactionsBorderColor ??
-                        Colors.transparent,
-                    backgroundColor: messageTheme?.reactionsBackgroundColor ??
+                    borderColor:
+                        messageTheme.reactionsBorderColor ?? Colors.transparent,
+                    backgroundColor: messageTheme.reactionsBackgroundColor ??
                         Colors.transparent,
                     maskColor: StreamChatTheme.of(context).colorTheme.white,
                     tailCirclesSpacing: 1,
diff --git a/packages/stream_chat_flutter/lib/src/message_text.dart b/packages/stream_chat_flutter/lib/src/message_text.dart
index eb80b89b..b0099eff 100644
--- a/packages/stream_chat_flutter/lib/src/message_text.dart
+++ b/packages/stream_chat_flutter/lib/src/message_text.dart
@@ -18,11 +18,11 @@ class MessageText extends StatelessWidget {
   final Message message;
   final void Function(User)? onMentionTap;
   final void Function(String)? onLinkTap;
-  final MessageTheme? messageTheme;
+  final MessageTheme messageTheme;
 
   @override
   Widget build(BuildContext context) {
-    final text = _replaceMentions(message.text)!.replaceAll('\n', '\\\n');
+    final text = _replaceMentions(message.text ?? '').replaceAll('\n', '\\\n');
 
     return MarkdownBody(
       data: text,
@@ -55,23 +55,23 @@ class MessageText extends StatelessWidget {
       styleSheet: MarkdownStyleSheet.fromTheme(
         Theme.of(context).copyWith(
           textTheme: Theme.of(context).textTheme.apply(
-                bodyColor: messageTheme!.messageText!.color,
-                decoration: messageTheme!.messageText!.decoration,
-                decorationColor: messageTheme!.messageText!.decorationColor,
-                decorationStyle: messageTheme!.messageText!.decorationStyle,
-                fontFamily: messageTheme!.messageText!.fontFamily,
+                bodyColor: messageTheme.messageText?.color,
+                decoration: messageTheme.messageText?.decoration,
+                decorationColor: messageTheme.messageText?.decorationColor,
+                decorationStyle: messageTheme.messageText?.decorationStyle,
+                fontFamily: messageTheme.messageText?.fontFamily,
               ),
         ),
       ).copyWith(
-        a: messageTheme!.messageLinks,
-        p: messageTheme!.messageText,
+        a: messageTheme.messageLinks,
+        p: messageTheme.messageText,
       ),
     );
   }
 
-  String? _replaceMentions(String? text) {
+  String _replaceMentions(String text) {
     message.mentionedUsers.map((u) => u.name).toSet().forEach((userName) {
-      text = text!.replaceAll(
+      text = text.replaceAll(
           '@$userName', '[@$userName](@${userName.replaceAll(' ', '')})');
     });
     return text;
diff --git a/packages/stream_chat_flutter/lib/src/message_widget.dart b/packages/stream_chat_flutter/lib/src/message_widget.dart
index 1e8049f8..b05762ba 100644
--- a/packages/stream_chat_flutter/lib/src/message_widget.dart
+++ b/packages/stream_chat_flutter/lib/src/message_widget.dart
@@ -66,7 +66,7 @@ class MessageWidget extends StatefulWidget {
   final Message message;
 
   /// The message theme
-  final MessageTheme? messageTheme;
+  final MessageTheme messageTheme;
 
   /// If true the widget will be mirrored
   final bool reverse;
@@ -93,7 +93,7 @@ class MessageWidget extends StatefulWidget {
   final EdgeInsetsGeometry? padding;
 
   /// The internal padding of the message text
-  final EdgeInsetsGeometry textPadding;
+  final EdgeInsets textPadding;
 
   /// The internal padding of an attachment
   final EdgeInsetsGeometry attachmentPadding;
@@ -222,7 +222,7 @@ class MessageWidget extends StatefulWidget {
                 child: wrapAttachmentWidget(
                   context,
                   Material(
-                    color: messageTheme?.messageBackgroundColor,
+                    color: messageTheme.messageBackgroundColor,
                     child: ImageGroup(
                       size: Size(
                         MediaQuery.of(context).size.width * 0.8,
@@ -425,7 +425,7 @@ class _MessageWidgetState extends State<MessageWidget>
   Widget build(BuildContext context) {
     super.build(context);
     final avatarWidth =
-        widget.messageTheme?.avatarTheme?.constraints.maxWidth ?? 40;
+        widget.messageTheme.avatarTheme?.constraints.maxWidth ?? 40;
     var leftPadding =
         widget.showUserAvatar != DisplayWidget.gone ? avatarWidth + 8.5 : 0.5;
 
@@ -544,7 +544,7 @@ class _MessageWidgetState extends State<MessageWidget>
                                                             BorderSide(
                                                               color: widget
                                                                       .messageTheme
-                                                                      ?.messageBorderColor ??
+                                                                      .messageBorderColor ??
                                                                   Colors.grey,
                                                             ),
                                                         borderRadius: widget
@@ -702,7 +702,7 @@ class _MessageWidgetState extends State<MessageWidget>
           ),
         InkWell(
           onTap: widget.onThreadTap != null ? onThreadTap : null,
-          child: Text(msg, style: widget.messageTheme?.replies),
+          child: Text(msg, style: widget.messageTheme.replies),
         ),
       ],
       if (showUsername)
@@ -710,13 +710,13 @@ class _MessageWidgetState extends State<MessageWidget>
           widget.message.user!.name,
           maxLines: 1,
           key: usernameKey,
-          style: widget.messageTheme?.messageAuthor,
+          style: widget.messageTheme.messageAuthor,
           overflow: TextOverflow.ellipsis,
         ),
       if (showTimeStamp)
         Text(
           Jiffy(widget.message.createdAt.toLocal()).jm,
-          style: widget.messageTheme?.createdAt,
+          style: widget.messageTheme.createdAt,
         ),
       if (showSendingIndicator) _buildSendingIndicator(),
     ]);
@@ -731,13 +731,13 @@ class _MessageWidgetState extends State<MessageWidget>
           Container(
             margin: EdgeInsets.only(
               bottom: context.textScaleFactor *
-                  ((widget.messageTheme?.replies?.fontSize ?? 1) / 2),
+                  ((widget.messageTheme.replies?.fontSize ?? 1) / 2),
             ),
             child: CustomPaint(
               size: Size(16, 32) * context.textScaleFactor,
               painter: _ThreadReplyPainter(
                 context: context,
-                color: widget.messageTheme?.messageBorderColor,
+                color: widget.messageTheme.messageBorderColor,
               ),
             ),
           ),
@@ -775,7 +775,7 @@ class _MessageWidgetState extends State<MessageWidget>
     return UrlAttachment(
       urlAttachment: urlAttachment,
       hostDisplayName: hostDisplayName,
-      textPadding: widget.textPadding as EdgeInsets,
+      textPadding: widget.textPadding,
     );
   }
 
@@ -830,12 +830,11 @@ class _MessageWidgetState extends State<MessageWidget>
                 key: ValueKey('${widget.message.id}.reactions'),
                 reverse: widget.reverse,
                 flipTail: widget.reverse,
-                backgroundColor:
-                    widget.messageTheme?.reactionsBackgroundColor ??
-                        Colors.transparent,
-                borderColor: widget.messageTheme?.reactionsBorderColor ??
+                backgroundColor: widget.messageTheme.reactionsBackgroundColor ??
                     Colors.transparent,
-                maskColor: widget.messageTheme?.reactionsMaskColor ??
+                borderColor: widget.messageTheme.reactionsBorderColor ??
+                    Colors.transparent,
+                maskColor: widget.messageTheme.reactionsMaskColor ??
                     Colors.transparent,
                 reactions: reactionsList,
               ),
@@ -1001,7 +1000,7 @@ class _MessageWidgetState extends State<MessageWidget>
   }
 
   Widget _buildSendingIndicator() {
-    final style = widget.messageTheme?.createdAt;
+    final style = widget.messageTheme.createdAt;
     final message = widget.message;
 
     if (hasNonUrlAttachments &&
@@ -1053,7 +1052,7 @@ class _MessageWidgetState extends State<MessageWidget>
           offset: Offset(
             0,
             widget.translateUserAvatar
-                ? (widget.messageTheme?.avatarTheme?.constraints.maxHeight ??
+                ? (widget.messageTheme.avatarTheme?.constraints.maxHeight ??
                         40) /
                     2
                 : 0,
@@ -1061,8 +1060,8 @@ class _MessageWidgetState extends State<MessageWidget>
           child: UserAvatar(
             user: widget.message.user!,
             onTap: widget.onUserAvatarTap,
-            constraints: widget.messageTheme?.avatarTheme!.constraints,
-            borderRadius: widget.messageTheme?.avatarTheme!.borderRadius,
+            constraints: widget.messageTheme.avatarTheme!.constraints,
+            borderRadius: widget.messageTheme.avatarTheme!.borderRadius,
             showOnlineStatus: false,
           ),
         ),
@@ -1085,9 +1084,9 @@ class _MessageWidgetState extends State<MessageWidget>
                     message: widget.message,
                     onMentionTap: widget.onMentionTap,
                     messageTheme: isOnlyEmoji
-                        ? widget.messageTheme?.copyWith(
+                        ? widget.messageTheme.copyWith(
                             messageText:
-                                widget.messageTheme?.messageText!.copyWith(
+                                widget.messageTheme.messageText!.copyWith(
                             fontSize: 42,
                           ))
                         : widget.messageTheme,
@@ -1103,7 +1102,7 @@ class _MessageWidgetState extends State<MessageWidget>
 
   Color? _getBackgroundColor() {
     if (hasQuotedMessage) {
-      return widget.messageTheme?.messageBackgroundColor;
+      return widget.messageTheme.messageBackgroundColor;
     }
 
     if (hasUrlAttachments) {
@@ -1118,7 +1117,7 @@ class _MessageWidgetState extends State<MessageWidget>
       return Colors.transparent;
     }
 
-    return widget.messageTheme?.messageBackgroundColor;
+    return widget.messageTheme.messageBackgroundColor;
   }
 
   void retryMessage(BuildContext context) {
diff --git a/packages/stream_chat_flutter/lib/src/quoted_message_widget.dart b/packages/stream_chat_flutter/lib/src/quoted_message_widget.dart
index bc77e97a..369fb4db 100644
--- a/packages/stream_chat_flutter/lib/src/quoted_message_widget.dart
+++ b/packages/stream_chat_flutter/lib/src/quoted_message_widget.dart
@@ -67,7 +67,7 @@ class QuotedMessageWidget extends StatelessWidget {
   final Message message;
 
   /// The message theme
-  final MessageTheme? messageTheme;
+  final MessageTheme messageTheme;
 
   /// If true the widget will be mirrored
   final bool reverse;
@@ -144,12 +144,12 @@ class QuotedMessageWidget extends StatelessWidget {
             child: MessageText(
               message: msg,
               messageTheme: isOnlyEmoji && _containsText
-                  ? messageTheme?.copyWith(
-                      messageText: messageTheme?.messageText?.copyWith(
+                  ? messageTheme.copyWith(
+                      messageText: messageTheme.messageText?.copyWith(
                       fontSize: 32,
                     ))
-                  : messageTheme?.copyWith(
-                      messageText: messageTheme?.messageText?.copyWith(
+                  : messageTheme.copyWith(
+                      messageText: messageTheme.messageText?.copyWith(
                       fontSize: 12,
                     )),
             ),
@@ -310,6 +310,6 @@ class QuotedMessageWidget extends StatelessWidget {
     if (_containsScrapeUrl) {
       return StreamChatTheme.of(context).colorTheme.blueAlice;
     }
-    return messageTheme?.messageBackgroundColor;
+    return messageTheme.messageBackgroundColor;
   }
 }
diff --git a/packages/stream_chat_flutter/lib/src/reaction_picker.dart b/packages/stream_chat_flutter/lib/src/reaction_picker.dart
index 7cd01eb7..cd358b2a 100644
--- a/packages/stream_chat_flutter/lib/src/reaction_picker.dart
+++ b/packages/stream_chat_flutter/lib/src/reaction_picker.dart
@@ -18,11 +18,9 @@ class ReactionPicker extends StatefulWidget {
   const ReactionPicker({
     Key? key,
     required this.message,
-    required this.messageTheme,
   }) : super(key: key);
 
   final Message message;
-  final MessageTheme? messageTheme;
 
   @override
   _ReactionPickerState createState() => _ReactionPickerState();
diff --git a/packages/stream_chat_flutter/lib/src/stream_chat.dart b/packages/stream_chat_flutter/lib/src/stream_chat.dart
index d3a196a1..d7e3ecea 100644
--- a/packages/stream_chat_flutter/lib/src/stream_chat.dart
+++ b/packages/stream_chat_flutter/lib/src/stream_chat.dart
@@ -32,7 +32,7 @@ import 'package:stream_chat_flutter_core/stream_chat_flutter_core.dart';
 /// Use [StreamChat.of] to get the current [StreamChatState] instance.
 class StreamChat extends StatefulWidget {
   final StreamChatClient client;
-  final Widget? child;
+  final Widget child;
   final StreamChatThemeData? streamChatThemeData;
 
   /// The amount of time that will pass before disconnecting the client in the background
@@ -96,7 +96,7 @@ class StreamChatState extends State<StreamChat> {
                 client: client,
                 onBackgroundEventReceived: widget.onBackgroundEventReceived,
                 backgroundKeepAlive: widget.backgroundKeepAlive,
-                child: widget.child!,
+                child: widget.child,
               ),
             );
           },
diff --git a/packages/stream_chat_flutter/lib/src/upload_progress_indicator.dart b/packages/stream_chat_flutter/lib/src/upload_progress_indicator.dart
index ec06de8a..e0e7e306 100644
--- a/packages/stream_chat_flutter/lib/src/upload_progress_indicator.dart
+++ b/packages/stream_chat_flutter/lib/src/upload_progress_indicator.dart
@@ -5,7 +5,7 @@ import 'stream_chat_theme.dart';
 class UploadProgressIndicator extends StatelessWidget {
   final int uploaded;
   final int total;
-  late final Color progressIndicatorColor;
+  final Color progressIndicatorColor;
   final EdgeInsetsGeometry padding;
   final bool showBackground;
   final TextStyle? textStyle;
@@ -14,7 +14,7 @@ class UploadProgressIndicator extends StatelessWidget {
     Key? key,
     required this.uploaded,
     required this.total,
-    Color? progressIndicatorColor,
+    this.progressIndicatorColor = const Color(0xffb2b2b2),
     this.padding = const EdgeInsets.only(
       top: 5,
       bottom: 5,
@@ -23,9 +23,7 @@ class UploadProgressIndicator extends StatelessWidget {
     ),
     this.showBackground = true,
     this.textStyle,
-  })  : progressIndicatorColor =
-            progressIndicatorColor ?? const Color(0xffb2b2b2),
-        super(key: key);
+  }) : super(key: key);
 
   @override
   Widget build(BuildContext context) {
diff --git a/packages/stream_chat_flutter/lib/src/url_attachment.dart b/packages/stream_chat_flutter/lib/src/url_attachment.dart
index d9beab20..e8e7b8a8 100644
--- a/packages/stream_chat_flutter/lib/src/url_attachment.dart
+++ b/packages/stream_chat_flutter/lib/src/url_attachment.dart
@@ -11,16 +11,21 @@ class UrlAttachment extends StatelessWidget {
   UrlAttachment({
     required this.urlAttachment,
     required this.hostDisplayName,
-    required this.textPadding,
+    this.textPadding = const EdgeInsets.symmetric(
+      horizontal: 16.0,
+      vertical: 8.0,
+    ),
   });
 
   @override
   Widget build(BuildContext context) {
     return GestureDetector(
-      onTap: () => launchURL(
-        context,
-        urlAttachment.ogScrapeUrl!,
-      ),
+      onTap: () {
+        launchURL(
+          context,
+          urlAttachment.ogScrapeUrl,
+        );
+      },
       child: Column(
         crossAxisAlignment: CrossAxisAlignment.stretch,
         children: [
diff --git a/packages/stream_chat_flutter/lib/src/utils.dart b/packages/stream_chat_flutter/lib/src/utils.dart
index ebb2a22e..79bd210e 100644
--- a/packages/stream_chat_flutter/lib/src/utils.dart
+++ b/packages/stream_chat_flutter/lib/src/utils.dart
@@ -22,10 +22,10 @@ Future<void> launchURL(BuildContext context, String? url) async {
 
 Future<bool?> showConfirmationDialog(
   BuildContext context, {
-  String? title,
+  required String title,
+  required String okText,
   Widget? icon,
   String? question,
-  String? okText,
   String? cancelText,
 }) {
   return showModalBottomSheet(
@@ -46,14 +46,15 @@ Future<bool?> showConfirmationDialog(
               if (icon != null) icon,
               SizedBox(height: 26.0),
               Text(
-                title!,
+                title,
                 style: StreamChatTheme.of(context).textTheme.headlineBold,
               ),
               SizedBox(height: 7.0),
-              Text(
-                question!,
-                textAlign: TextAlign.center,
-              ),
+              if (question != null)
+                Text(
+                  question,
+                  textAlign: TextAlign.center,
+                ),
               SizedBox(height: 36.0),
               Container(
                 color: effect.color!.withOpacity(effect.alpha ?? 1),
@@ -61,27 +62,28 @@ Future<bool?> showConfirmationDialog(
               ),
               Row(
                 children: [
-                  Flexible(
-                    child: Container(
-                      alignment: Alignment.center,
-                      child: TextButton(
-                        onPressed: () {
-                          Navigator.of(context).pop(false);
-                        },
-                        child: Text(
-                          cancelText!,
-                          style: StreamChatTheme.of(context)
-                              .textTheme
-                              .bodyBold
-                              .copyWith(
-                                  color: StreamChatTheme.of(context)
-                                      .colorTheme
-                                      .black
-                                      .withOpacity(0.5)),
+                  if (cancelText != null)
+                    Flexible(
+                      child: Container(
+                        alignment: Alignment.center,
+                        child: TextButton(
+                          onPressed: () {
+                            Navigator.of(context).pop(false);
+                          },
+                          child: Text(
+                            cancelText,
+                            style: StreamChatTheme.of(context)
+                                .textTheme
+                                .bodyBold
+                                .copyWith(
+                                    color: StreamChatTheme.of(context)
+                                        .colorTheme
+                                        .black
+                                        .withOpacity(0.5)),
+                          ),
                         ),
                       ),
                     ),
-                  ),
                   Flexible(
                     child: Container(
                       alignment: Alignment.center,
@@ -90,7 +92,7 @@ Future<bool?> showConfirmationDialog(
                           Navigator.pop(context, true);
                         },
                         child: Text(
-                          okText!,
+                          okText,
                           style: StreamChatTheme.of(context)
                               .textTheme
                               .bodyBold
@@ -112,10 +114,10 @@ Future<bool?> showConfirmationDialog(
 
 Future<bool?> showInfoDialog(
   BuildContext context, {
-  String? title,
+  required String title,
+  required String okText,
   Widget? icon,
   String? details,
-  String? okText,
   StreamChatThemeData? theme,
 }) {
   return showModalBottomSheet(
@@ -140,14 +142,14 @@ Future<bool?> showInfoDialog(
               height: 26.0,
             ),
             Text(
-              title!,
+              title,
               style: theme?.textTheme.headlineBold ??
                   StreamChatTheme.of(context).textTheme.headlineBold,
             ),
             SizedBox(
               height: 7.0,
             ),
-            Text(details!),
+            if (details != null) Text(details),
             SizedBox(
               height: 36.0,
             ),
@@ -162,7 +164,7 @@ Future<bool?> showInfoDialog(
                   Navigator.of(context).pop();
                 },
                 child: Text(
-                  okText!,
+                  okText,
                   style: TextStyle(
                     color: theme?.colorTheme.black.withOpacity(0.5) ??
                         StreamChatTheme.of(context).colorTheme.accentBlue,
diff --git a/packages/stream_chat_flutter/lib/src/video_thumbnail_image.dart b/packages/stream_chat_flutter/lib/src/video_thumbnail_image.dart
index df8373eb..3d9d5429 100644
--- a/packages/stream_chat_flutter/lib/src/video_thumbnail_image.dart
+++ b/packages/stream_chat_flutter/lib/src/video_thumbnail_image.dart
@@ -9,7 +9,7 @@ import 'stream_svg_icon.dart';
 import 'video_service.dart';
 
 class VideoThumbnailImage extends StatefulWidget {
-  final String? video;
+  final String video;
   final double? width;
   final double? height;
   final BoxFit? fit;
@@ -38,7 +38,7 @@ class _VideoThumbnailImageState extends State<VideoThumbnailImage> {
   @override
   void initState() {
     thumbnailFuture = VideoService.generateVideoThumbnail(
-      video: widget.video!,
+      video: widget.video,
       imageFormat: widget.format,
     );
     super.initState();
@@ -48,7 +48,7 @@ class _VideoThumbnailImageState extends State<VideoThumbnailImage> {
   void didUpdateWidget(covariant VideoThumbnailImage oldWidget) {
     if (oldWidget.video != widget.video || oldWidget.format != widget.format) {
       thumbnailFuture = VideoService.generateVideoThumbnail(
-        video: widget.video!,
+        video: widget.video,
         imageFormat: widget.format,
       );
     }
diff --git a/packages/stream_chat_flutter/test/src/attachment_actions_modal_test.dart b/packages/stream_chat_flutter/test/src/attachment_actions_modal_test.dart
index 361d7cfc..762d4fe9 100644
--- a/packages/stream_chat_flutter/test/src/attachment_actions_modal_test.dart
+++ b/packages/stream_chat_flutter/test/src/attachment_actions_modal_test.dart
@@ -278,7 +278,7 @@ void main() {
           builder: (context, child) {
             return StreamChat(
               client: client,
-              child: child,
+              child: child!,
             );
           },
           home: StreamChannel(
@@ -331,7 +331,7 @@ void main() {
           builder: (context, child) {
             return StreamChat(
               client: client,
-              child: child,
+              child: child!,
             );
           },
           home: StreamChannel(
@@ -381,7 +381,7 @@ void main() {
           builder: (context, child) {
             return StreamChat(
               client: client,
-              child: child,
+              child: child!,
             );
           },
           home: StreamChannel(
@@ -415,7 +415,7 @@ void main() {
           builder: (context, child) {
             return StreamChat(
               client: client,
-              child: child,
+              child: child!,
             );
           },
           home: Container(
@@ -472,7 +472,7 @@ void main() {
           builder: (context, child) {
             return StreamChat(
               client: client,
-              child: child,
+              child: child!,
             );
           },
           home: Container(
diff --git a/packages/stream_chat_flutter/test/src/message_action_modal_test.dart b/packages/stream_chat_flutter/test/src/message_action_modal_test.dart
index 8a6e8c33..0be509ae 100644
--- a/packages/stream_chat_flutter/test/src/message_action_modal_test.dart
+++ b/packages/stream_chat_flutter/test/src/message_action_modal_test.dart
@@ -264,7 +264,7 @@ void main() {
             return StreamChat(
               client: client,
               streamChatThemeData: streamTheme,
-              child: child,
+              child: child!,
             );
           },
           theme: themeData,
@@ -314,7 +314,7 @@ void main() {
             return StreamChat(
               client: client,
               streamChatThemeData: streamTheme,
-              child: child,
+              child: child!,
             );
           },
           theme: themeData,
@@ -369,7 +369,7 @@ void main() {
             return StreamChat(
               client: client,
               streamChatThemeData: streamTheme,
-              child: child,
+              child: child!,
             );
           },
           theme: themeData,
@@ -420,7 +420,7 @@ void main() {
             return StreamChat(
               client: client,
               streamChatThemeData: streamTheme,
-              child: child,
+              child: child!,
             );
           },
           theme: themeData,
@@ -471,7 +471,7 @@ void main() {
             return StreamChat(
               client: client,
               streamChatThemeData: streamTheme,
-              child: child,
+              child: child!,
             );
           },
           theme: themeData,
@@ -520,7 +520,7 @@ void main() {
             return StreamChat(
               client: client,
               streamChatThemeData: streamTheme,
-              child: child,
+              child: child!,
             );
           },
           theme: themeData,
@@ -579,7 +579,7 @@ void main() {
             return StreamChat(
               client: client,
               streamChatThemeData: streamTheme,
-              child: child,
+              child: child!,
             );
           },
           theme: themeData,
@@ -638,7 +638,7 @@ void main() {
             return StreamChat(
               client: client,
               streamChatThemeData: streamTheme,
-              child: child,
+              child: child!,
             );
           },
           theme: themeData,
@@ -693,7 +693,7 @@ void main() {
             return StreamChat(
               client: client,
               streamChatThemeData: streamTheme,
-              child: child,
+              child: child!,
             );
           },
           theme: themeData,
@@ -752,7 +752,7 @@ void main() {
             return StreamChat(
               client: client,
               streamChatThemeData: streamTheme,
-              child: child,
+              child: child!,
             );
           },
           theme: themeData,