Avoid trying to set room account data for pinned events as guest (#11216)

src/components/views/right_panel/PinnedMessagesCard.tsx

@@ -103,10 +103,11 @@ const PinnedMessagesCard: React.FC<IProps> = ({ room, onClose, permalinkCreator
     const readPinnedEvents = useReadPinnedEvents(room);
 
     useEffect(() => {
+        if (!cli || cli.isGuest()) return; // nothing to do
         const newlyRead = pinnedEventIds.filter((id) => !readPinnedEvents.has(id));
         if (newlyRead.length > 0) {
             // clear out any read pinned events which no longer are pinned
-            cli?.setRoomAccountData(room.roomId, ReadPinsEventId, {
+            cli.setRoomAccountData(room.roomId, ReadPinsEventId, {
                 event_ids: pinnedEventIds,
             });
         }