title: UIActivityViewController not working after Cancel
body: <p>I am using an instance of <code>UIActivityViewController</code> in a universal app. It works absolutely perfectly on the iPad. Nearly, but not quite on the iPhone.</p>
  
  <p>I present it using:</p>
  
  <pre><code>    [self presentViewController:self.activityViewController animated:YES completion:nil];
  </code></pre>
  
  <p>It displays the available activities correctly and if I choose one, it works. I can then tap on the Share button again and repeat with the same or a different activity as often as I like, so long as I complete the activity.</p>
  
  <p>If I Cancel from the <code>UIActivityViewController</code>, all is well; but if I cancel from, say, Mail or Message, the next time I tap on Share, nothing happens. If I get impatient and tap again, I get the following error:</p>
  
  <p>'Application tried to present modally an active controller .'</p>
  
  <p>I've tried dismissing the controller before presenting it a second time, but it doesn't think it is dismissible. I've also tried presenting it from the root/navigation controller as well as the tableviewcontroller, but get the equivalent error (i.e. the app tried to present the root controller).</p>
  
  <p>I see there are lots of 'odd' problems with <code>UIActivityViewController</code>, but I can't see anything relevant to my problem.</p>