Hide unknown event types

lib/components/list_items/message.dart

@@ -33,6 +33,9 @@ class Message extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    if (event.type == EventTypes.Unknown) {
+      return Container();
+    }
     if (![EventTypes.Message, EventTypes.Sticker, EventTypes.Encrypted]
         .contains(event.type)) {
       return StateMessage(event);