Fix a bug

Signed-off-by: Mario Danic <mario@lovelyhq.com>

app/src/main/java/com/nextcloud/talk/controllers/ChatController.java

@@ -229,7 +229,7 @@ public class ChatController extends BaseController implements MessagesListAdapte
                             }
                         }
 
-                        setupMentionAutocomplete();
+                        getActivity().runOnUiThread(() -> setupMentionAutocomplete());
                         joinRoomWithPassword();
                     }