message: Fix timeline & notifs panel spuriously being empty
  Only claim there's nothing to display once we've failed to back
  paginate, otherwise we'll show the empty message instead of the
  MessagePanel and therefore never try to back-paginate.
diff: @@ -993,7 +993,7 @@ var TimelinePanel = React.createClass({
  );
  }
  - if (this.state.events.length == 0) {
  + if (this.state.events.length == 0 && !this.state.canBackPaginate && this.props.empty) {
  return (
  <div className={ this.props.className + " mx_RoomView_messageListWrapper" }>
  <div className="mx_RoomView_empty">{ this.props.empty }</div>
  