title: UIAlertController crash for being presented in backgroundThread objective C
body: <p>I have been using <code>UIAlertController</code> in previous apps but I am facing a strange error this time. Here is my code which I using to present it:</p>
  
  <pre><code>     UIAlertController *alertController = [UIAlertController alertControllerWithTitle:ALERT_TITLE_STRING message:message preferredStyle:UIAlertControllerStyleAlert];
       [alertController addAction:[UIAlertAction actionWithTitle:OK_STRING style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
  
       }]];
       [[[[UIApplication sharedApplication] keyWindow] rootViewController] presentViewController:alertController animated:YES completion:^{
  
       }];
  </code></pre>
  
  <p>Everything was fine but now I my app crashes on last line. Here is error:</p>
  
  <blockquote>
    <p>This application is modifying the autolayout engine from a background
    thread, which can lead to engine corruption and weird crashes.  This
    will cause an exception in a future release.</p>
  </blockquote>
  
  <p>I am not using <code>autolayout</code> in my app. I have no idea why I am getting this error.</p>
  
  <p>Any clues? </p>