iOS crash when presenting view controller after dialog display

gistfile1.txt

  // the fact that alertView is retained here seems important -- does not reproduce otherwise.
  self.alertView = [[UIAlertView alloc] initWithTitle: @"OK" message: @"OK" delegate: nil cancelButtonTitle: @"Cancel" otherButtonTitles: nil];
  [self.alertView show];

  // White the dialog is open, present a modal view controller.  In a real-world scenario, this is actually
  // occurring when the view controller is presented in response to alertView:clickedButtonAtIndex:, but
  // for this example, we'll do it automatically.
  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
    UIViewController *controller = [[UIViewController alloc] initWithNibName: nil bundle: nil];
    controller.view = [[UIView alloc] initWithFrame: CGRectMake(0, 0, 320, 480)];
    controller.view.backgroundColor = [UIColor greenColor];

    [self.root presentViewController: controller animated: YES completion: nil];
  });

  // Dismiss the alert via simulating a button click.
  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
      [self.alertView dismissWithClickedButtonIndex: 1 animated:YES];
  });

  // Dismiss the view controller.
  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
      [self.window.rootViewController dismissViewControllerAnimated: YES completion: nil];
  });

  // Set the status bar to hidden and a crash results.
  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(4.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
    [[UIApplication sharedApplication] setStatusBarHidden: YES];
  });