Check existence of timeline state in community timeline (#11880)

app/javascript/mastodon/features/community_timeline/index.js

@@ -18,9 +18,10 @@ const mapStateToProps = (state, { onlyMedia, columnId }) => {
   const uuid = columnId;
   const columns = state.getIn(['settings', 'columns']);
   const index = columns.findIndex(c => c.get('uuid') === uuid);
+  const timelineState = state.getIn(['timelines', `community${onlyMedia ? ':media' : ''}`]);
 
   return {
-    hasUnread: state.getIn(['timelines', `community${onlyMedia ? ':media' : ''}`, 'unread']) > 0 || state.getIn(['timelines', `community${onlyMedia ? ':media' : ''}`, 'pendingItems']).size > 0,
+    hasUnread: !!timelineState && (timelineState.get('unread') > 0 || timelineState.get('pendingItems').size > 0),
     onlyMedia: (columnId && index >= 0) ? columns.get(index).getIn(['params', 'other', 'onlyMedia']) : state.getIn(['settings', 'community', 'other', 'onlyMedia']),
   };
 };