fix #6: ChannelListView NULL error when a channel has no messages

lib/src/message_widget.dart

@@ -93,7 +93,7 @@ class _MessageWidgetState extends State<MessageWidget>
     final alignment =
         _isMyMessage ? Alignment.centerRight : Alignment.centerLeft;
 
-    List<Widget> row = <Widget>[
+    var row = <Widget>[
       Column(
         crossAxisAlignment:
             _isMyMessage ? CrossAxisAlignment.end : CrossAxisAlignment.start,
@@ -302,7 +302,7 @@ class _MessageWidgetState extends State<MessageWidget>
     }));
 
     if (widget.message.text.trim().isNotEmpty) {
-      String text = widget.message.text;
+      var text = widget.message.text;
       text = _replaceMentions(text);
 
       column.addAll(