title: -(void)gameCenterViewControllerDidFinish:(GKGameCenterViewController *)gameCenterViewController not been called
body: <p>As in the title, I do not manage to have that callback called in order to dismiss the game center view controller neither on my iOS 7 iPhone nor iOS 8 iPad. This is the code I use:</p>
  
  <pre><code>GKGameCenterViewController *controller=nil;
  
  - (IBAction)achievementButtonClicked:(id)sender {
      if (!controller){
          controller=[[GKGameCenterViewController alloc] init];
          controller.delegate=self;
      }
      NSLog(@"controller=%@", controller);
      if (controller) [self presentViewController:controller animated:YES completion:nil];
  }
  
  -(void)gameCenterViewControllerDidFinish:(GKGameCenterViewController *)gameCenterViewController{
      [gameCenterViewController dismissViewControllerAnimated:YES completion:nil];
  
     // I also tried [self dismissViewControllerAnimated:YES completion:nil] but anyway the function seems to not even enter here
  }
  </code></pre>
  
  <p>If I take the function off, the delegate complaints it is missing, so the issue should not be connected to that. What might that be and how to fix it?</p>