Check if fragment already has a view and is still attached

app/src/main/java/chat/rocket/android/chatroom/ui/ChatRoomFragment.kt

@@ -276,10 +276,12 @@ class ChatRoomFragment : Fragment(), ChatRoomView, EmojiKeyboardListener, EmojiR
     ) {
         // TODO: We should rely solely on the user being able to post, but we cannot guarantee
         // that the "(channels|groups).roles" endpoint is supported by the server in use.
+        ui {
             setupMessageComposer(userCanPost)
             isBroadcastChannel = channelIsBroadcast
             if (isBroadcastChannel && !userCanMod) activity?.invalidateOptionsMenu()
         }
+    }
 
     override fun openDirectMessage(chatRoom: ChatRoom, permalink: String) {