title: When UINavigationController is modally presented via Storyboards, it's rootViewController has no connection to it
body: <p>My storyboard looks like this:
  <img src="https://i.stack.imgur.com/BS0nv.png" alt="enter image description here"></p>
  
  <p>The first part works prefect, the problem is that when I use the "Test Modal" button to modally show the second NavigationController, that is correctly set up to have a rootViewController - the connection is not being made.</p>
  
  <p>Meaning, I <em>know</em> the UINavigationController is there (with querying all controllers starting from the UIWindow's rootViewController), and my controller is also loaded, but navigationController is nil, parentViewController is nil - there's no way I could access the UINavigationController (and thus no way to customize the top toolbar)</p>
  
  <p>If I check the "Is Initial View Controller" on the second UINavigationController, it works (but obviously that's not what I want). I believe this might be a UIKit bug. Or am I doing it wrong?</p>