title: Custom animation for UINavigationController push not rendering navbar correctly
body: <p>In a custom segue, I have the following simple transition:</p>
  
  <pre><code>- (void) perform {
      UIViewController *src = (UIViewController *) self.sourceViewController;
      UIViewController *dst = (UIViewController *) self.destinationViewController;
      [UIView transitionWithView:src.navigationController.view duration:1
                         options:UIViewAnimationOptionTransitionFlipFromBottom
                      animations:^{
                          [src.navigationController pushViewController:dst animated:NO];
                      }
                      completion:NULL];
  }
  </code></pre>
  
  <p>The content view animates fine. However, when executing the animation, the nav bar at the top has a messed up layout (buttons all crammed in the upper left corner, no title), popping into place only when the animation is finished.  Anyone know what I've done wrong and how to fix it?  Thanks!</p>