message: update initially shown amount of tiles on component update
  as rooms aren't all available at ctor time
diff: @@ -142,7 +142,11 @@ export default class RoomSublist2 extends React.Component<IProps, IState> {
  }
  private get numTiles(): number {
  - return (this.props.rooms || []).length + (this.props.extraBadTilesThatShouldntExist || []).length;
  + return RoomSublist2.calcNumTiles(this.props);
  + }
  +
  + private static calcNumTiles(props) {
  + return (props.rooms || []).length + (props.extraBadTilesThatShouldntExist || []).length;
  }
  private get numVisibleTiles(): number {
  @@ -150,8 +154,13 @@ export default class RoomSublist2 extends React.Component<IProps, IState> {
  return Math.min(nVisible, this.numTiles);
  }
  - public componentDidUpdate() {
  + public componentDidUpdate(prevProps) {
  this.state.notificationState.setRooms(this.props.rooms);
  + // as the rooms can come in one by one we need to reevaluate
  + // the amount of available rooms to cap the amount of requested visible rooms by the layout
  + if (RoomSublist2.calcNumTiles(prevProps) !== this.numTiles) {
  + this.setState({height: this.calculateInitialHeight()});
  + }
  }
  public componentWillUnmount() {
  