message: Initialise last_rm_sent_event_id
diff: @@ -174,6 +174,7 @@ var TimelinePanel = React.createClass({
  debuglog("TimelinePanel: mounting");
  this.last_rr_sent_event_id = undefined;
  + this.last_rm_sent_event_id = undefined;
  this.dispatcherRef = dis.register(this.onAction);
  MatrixClientPeg.get().on("Room.timeline", this.onRoomTimeline);
  