message: Fix filtering causing sticky header artifacts
  In we reduced the RoomList updates to just added/removed sublists, but didn't consider that we might also have to handle lengths of those sublists changing enough for us to fix the sticky headers.
diff: @@ -239,7 +239,22 @@ export default class RoomList extends React.Component<IProps, IState> {
  const previousListIds = Object.keys(this.state.sublists);
  const newListIds = Object.keys(newLists);
  - if (arrayHasDiff(previousListIds, newListIds)) {
  + let doUpdate = arrayHasDiff(previousListIds, newListIds);
  + if (!doUpdate) {
  + // so we didn't have the visible sublists change, but did the contents of those
  + // sublists change significantly enough to break the sticky headers? Probably, so
  + // let's check the length of each.
  + for (const tagId of newListIds) {
  + const oldRooms = this.state.sublists[tagId];
  + const newRooms = newLists[tagId];
  + if (oldRooms.length !== newRooms.length) {
  + doUpdate = true;
  + break;
  + }
  + }
  + }
  +
  + if (doUpdate) {
  this.setState({sublists: newLists}, () => {
  this.props.onResize();
  });
  