I am following a simple swift tutorial that shows how to add a navigation controller to a viewcontroller in storyboards in xcode. This is done using Editor > Embed in > Navigation Controller
The problem is, once the navigation controller is embedded, it cannot be removed. The 'unembed' option is always greyed out. Removing the controller view from the storyboard results in an error. Even if the arrow indicating the first view is pointing to a simple empty view in exactly the same way as when you're starting a new project.
I would expect that there is still some code from the Navigation Controller lingering around somewhere, but how to pinpoint it?