title: QLPreviewController delegate method doesn't get called in iOS 10, but does get called if ran earlier than iOS 10
body: <p>Here is my code. This may sound like redundant question but my scenario is different as I am not adding QLPreviewController as a subview but present as a controller.</p>
  
  <p>After downloading from dropbox, I present it like-</p>
  
  <pre><code>    self.pdfViewController = [[QLPreviewController alloc] init];
      self.pdfViewController.delegate = self;
      self.pdfViewController.dataSource = self;
  
      [self presentViewController:self.pdfViewController animated:YES completion:nil];
  </code></pre>
  
  <p>and I also have <code>QLPreviewControllerDataSource, QLPreviewControllerDelegate</code> listed as the protocol. Besides, it is working if being run in earlier than iOS 10.0.</p>
  
  <p>Please help me.</p>