Problems when adding Navigation Controller

[derwaldgeist]

I sucessfully patched the Swift version to the new Swift 2 syntax. Everything works in principle, but only if I place the picker inside a normal view controller. Once I add a navigation controller, I'm getting error messages:

"Please check the values return by the delegate. The behavior of the UICollectionViewFlowLayout is not defined because: The item height must be less than the height of the UICollectionView minus the section insets top and bottom values."

This happens despite the picker has a size big enough to incorporate all items.

On screen, the problem is that the very last item is positioned below all other items, with an additional spacing to the top. This is why the space is not sufficient for everything. But this only happens when there is a navigation controller active.