title: Can't drag button action to existing function in Xcode 8
body: <p>I have a weird issue with Xcode 8. When I try to ctrl + drag button to existing function, I can't I can only create new outlet or Action. What is more weird, that even when I create action by ctrl + drag i can't connect event the same button that I used for creating action. IB icon is also blank like there is no connection between action and button, but real time clicking runs action.
  On the other hand when I try to connect action to button from swift to storyboard I can (@IB icon becomes "full"), but then I get exception on real time clicking unrecognized selector myActionWithSender
  <a href="https://i.stack.imgur.com/bcTQ1.gif" rel="noreferrer"><img src="https://i.stack.imgur.com/bcTQ1.gif" alt="enter image description here"></a>
  <a href="https://i.stack.imgur.com/dBiou.gif" rel="noreferrer"><img src="https://i.stack.imgur.com/dBiou.gif" alt="enter image description here"></a></p>