title: SKStoreProductViewControllerDelegate method not being called
body: <p>I'm simply trying to implement the iTunes store screen in my application, and it displays correctly. However, when the user is finished with the screen (makes a purchase or clicks 'cancel') all I get is a white screen, and I have to completely close my app and reopen it.</p>
  
  <p>It turns out my <code>productViewControllerDidFinish</code> method isn't being called. </p>
  
  <p>I have a table view controller that has the SKStoreProductViewControllerDelegate and I'm presenting and dismissing the store view in the same class, so why isn't the delegate method being called?</p>
  
  <pre><code>- (void)toStore:(Button*)sender {
      SKStoreProductViewController *storeProductViewController = [[SKStoreProductViewController alloc] init];
      [storeProductViewController loadProductWithParameters:@{SKStoreProductParameterITunesItemIdentifier : @"stuff"} completionBlock:^(BOOL result, NSError *error) {
          if (error) {
              NSLog(@"Error %@ with User Info %@.", error, [error userInfo]);
  
          } else {
              [self presentViewController:storeProductViewController animated:YES completion:nil];
          }
      }];
  }
  
  - (void)productViewControllerDidFinish:(SKStoreProductViewController*)viewController {
      [self dismissViewControllerAnimated:YES completion:nil];
  }
  </code></pre>
  
  <p>Both in a UITableViewController. Thanks in advance!</p>