message: Don't show "Drop to ..." if total rooms = 0
diff: @@ -540,6 +540,10 @@ module.exports = React.createClass({
  }
  }
  + if (this.state.totalRoomCount === 0) {
  + return null;
  + }
  +
  const labelText = 'Drop here to ' + (VERBS[section] || 'tag ' + section);
  return <RoomDropTarget label={labelText} />;
  