title: "Add Documentation" is disabled in Xcode 9.1 (9B55)
body: <p>For example:</p>
  
  <p><a href="https://i.stack.imgur.com/G1NcZ.png" rel="noreferrer"><img src="https://i.stack.imgur.com/G1NcZ.png" alt="Add Documentation Disabled"></a></p>
  
  <p>Any ideas?</p>
  
  <p>MacOS High Sierra 10.13.1<br>
  Xcode 9.1 9B55</p>