title: popToViewController presenting a black view
body: <p>I have an app that has many different views. The entry point to the app is the home page where I have 2 buttons (note that the home page is embedded in a navigation controller). Each button leads to a new stack of views, I tried embedding the first view of those stacks into a navigation controller, but when I push a button on the home page that leads to a new stack, the app crashes giving me a "Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Pushing a navigation controller is not supported'" message. So I avoided embedding the stacks into a nav controller. The problem happens when I push the save button in the last view of the stack. In there I did the usual </p>
  
  <pre><code>self.navigationController?.popToViewController(firstViewController, animated: true)
  </code></pre>
  
  <p>This does not work and I get sent to the firstViewController, however the navigation bar buttons don't show up, the background is black and nothing shows. If I popToRootViewController however, it works. Cheers!</p>