feat: added customization options in main widgets (#312)

* polish channelpreview customization options

* polish channelheader customization options

* polish messageinput customization options

* polish threadheader customization options

* polish channellistheader customization options

* show the parent message if no messages in thread

* fix edit message

* fix channelinfo textstyle

* fix review

* fix useravatar

* add ontitle tap to thread header

* add custom message actions

* add borderradius and button builder

* add ontap to messageinput custom send button

* fix bottom sheet

* add doc

* use placeholder image

* add doc

* fix listtile density

* remove subtitle from ChannelListHeaderTheme.copyWith

* add InputDecoration.merge extension

packages/stream_chat_flutter_core/lib/src/channels_bloc.dart

@@ -172,11 +172,14 @@ class ChannelsBlocState extends State<ChannelsBloc>
     }));
 
     _subscriptions.add(client
-        .on(EventType.channelDeleted, EventType.notificationRemovedFromChannel)
+        .on(
+      EventType.channelDeleted,
+      EventType.notificationRemovedFromChannel,
+    )
         .listen((e) {
       final channel = e.channel;
-      _channelsController
-          .add(List.from(channels..removeWhere((c) => c.cid == channel.cid)));
+      _channelsController.add(List.from(
+          (channels ?? [])..removeWhere((c) => c.cid == channel.cid)));
     }));
   }
 

packages/stream_chat_flutter_core/lib/src/message_list_core.dart

@@ -144,7 +144,7 @@ class _MessageListCoreState extends State<MessageListCore> {
           return widget.errorWidgetBuilder(context, snapshot.error);
         } else {
           final messageList = snapshot.data?.reversed?.toList() ?? [];
-          if (messageList.isEmpty) {
+          if (messageList.isEmpty && !_isThreadConversation) {
             if (_upToDate) {
               return widget.emptyBuilder(context);
             }