message: Show "jump to message" when message is not paginated
diff: @@ -1280,7 +1280,8 @@ module.exports = React.createClass({
  // we want to show the bar if the read-marker is off the top of the
  // screen.
  - var showBar = (pos < 0);
  + // If pos is null, the event might not be paginated, so show the unread bar!
  + var showBar = pos < 0 || pos === null;
  if (this.state.showTopUnreadMessagesBar != showBar) {
  this.setState({showTopUnreadMessagesBar: showBar},
  