title: Interface Builder can't set accessibility traits (Xcode 8)
body: <p>I am having a weird problem in Interface Builder (Xcode 8). Basically, I can't enable (select) accessibility traits; IB is rejecting my attempt.</p>
  
  <p>For example, I have a UILabel which has the "static text" and "user interaction enabled" traits enabled. I can click the "static text" checkbox to disable it. But then when I click it again to re-enable it, the checkbox briefly shows a minus ("-") which then disappears, leaving the checkbox unchecked.</p>
  
  <p>I don't know how to re-enable that checkbox (or any other). Any solutions would be appreciated!</p>