title: How to jump to any ViewController in another UINavigationController
body: <p>I have a project created with a storyboard. There I have many ViewControllers, connected with segues. Now I want to get from ViewController (VC in the following) A , which is embedded in a navigationController (as RootVC) and presented with a modal segue by another VC B (which is also presented by another VC C modally) to any other VC D in the storyboard (In this case the first one in the main Navigation Controller E). 
  I experienced that the NavigationController hierarchy is "destroyed" by a  modal segue, and because I need the function to use push segue in VC A, I need to use a second NavigationController... I've already tried to save an instance of the destination VC D globally and then jump there with</p>
  
  <pre><code>    self.navigationController.popToViewController(myDestinationVC_D, animated: true)
  </code></pre>
  
  <p>But then I get an error because of a nil-optional that was unpacked.</p>
  
  <p>I hope you can help me. I think the given information should be enough, but if you need more, just comment. (I hope my English is not too bad ;))
  Thank you !</p>