title: Possible to use UIAlertController on a modal view controller?
body: <p>I have a presented (modal) view controller that needs to present an action sheet. However when I do this: </p>
  
  <pre><code>UIAlertController *actionSheet = [UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleActionSheet];
  
  ...
  
  [self presentViewController:actionSheet animated:YES completion:nil];
  </code></pre>
  
  <p>I get this:</p>
  
  <pre><code>Warning: Attempt to present &lt;UIAlertController: 0x7fed4a608120&gt;  on &lt;MyViewController: 0x7fed4d1ca520&gt; which is already presenting (null)
  </code></pre>
  
  <p>Is there a workaround here? It seems like a pretty common scenario to use an alert or action sheet from a presented view controller.</p>