title: iOS Unwind Segue stops working when embedded in a navigation controller
body: <p>I have a UIViewController which has a button that performs a modal segue to a UIViewController as a Form Sheet.  On that form sheet is a cancel button with an unwind segue back to the original UIViewController.  This seems to work perfectly happily and dismisses the form sheet.</p>
  
  <p>As soon as I select the original UIViewController and select the option in XCode to Embed in a Navigation Controller, the unwind segue no longer seems to work and the modal form sheet will no longer cancel.</p>
  
  <p>I'm sure there is a simple explanation, but it is currently evading me, so any thoughts welcomed.</p>
  
  <p>Thanks.</p>