Handle MPInterstitialAdController was dismissed from rootviewcontroller


How can I handle event, when MPInterstitialAdController was dismissed from rootviewcontroller? Method interstitialDidDisappear: called when MPInterstitialAdController begin to disappear. I want to handle the event when MPInterstitialAdController finally disappear from rootviewcontroller and I can show other modal view controller.
If I try show other modal viewcontroller in interstitialDidDisappear: …

- (void)interstitialDidDisappear:(MPInterstitialAdController *)interstitial {
    MPMoviePlayerViewController* sampleController = [[MPMoviePlayerViewController alloc] 
                                               initWithContentURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"example" ofType:@"mp4"]]];
    [self presentViewController:sampleController animated:NO completion:^{ }];

… i get warning

Warning: Attempt to present <MPMoviePlayerViewController: 0x19f1940> on <RootViewController: 0x1a5cb40> while a presentation is in progress!