message: Null-guard roomId before sending a dispatch to update scroll state
  Otherwise we pointlessly assign the null key to something
diff: @@ -590,6 +590,10 @@ module.exports = React.createClass({
  },
  _updateScrollMap(roomId) {
  + // No point updating scroll state if the room ID hasn't been resolved yet
  + if (!roomId) {
  + return;
  + }
  dis.dispatch({
  action: 'update_scroll_state',
  room_id: roomId,
  