message: Fix bug where `roomId` was expected to be a property on timelineSet
diff: @@ -734,7 +734,7 @@ var TimelinePanel = React.createClass({
  // the messagePanel doesn't know where the read marker is.
  // if we know the timestamp of the read marker, make a guess based on that.
  - var rmTs = TimelinePanel.roomReadMarkerTsMap[this.props.timelineSet.roomId];
  + const rmTs = TimelinePanel.roomReadMarkerTsMap[this.props.timelineSet.room.roomId];
  if (rmTs && this.state.events.length > 0) {
  if (rmTs < this.state.events[0].getTs()) {
  return -1;
  