fix review

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,
               ),
           ],
         ),

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(

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,

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,