title: Checking if a ViewController on Navigation Stack exists
body: <p>I have this code here to check on the existence of the <code>ViewController</code>. And unfortunately it doesn't work. The thing is, it is executed <em>at the moment</em> of another VC popping from the <code>Navigation Stack</code>:</p>
  
  <pre><code>- (void) leftViewDidHide{
      if ([((AppDelegate *)[UIApplication sharedApplication].delegate).frontViewController.navigationController.viewControllers objectAtIndex:1]) {
      SGServerListViewController *sample = [[[((AppDelegate *)[UIApplication sharedApplication].delegate).frontViewController.navigationController.viewControllers objectAtIndex:1]childViewControllers] objectAtIndex:0];
      [sample.serverTableView setUserInteractionEnabled:YES];
      }
  }
  </code></pre>
  
  <p>The app crashes with an exception breakpoint pointing me to the line with an <code>if</code> statement. Any ideas on what could be wrong here? I'm just trying to check if this <code>VC</code> is there and if it is - execute the code.</p>