title: StoryBoard Assistant Editor stopped showing associated file
body: <p>Xcode storyboard assistant editor stopped showing related files.
  "Automatic" is selected and "Class" is filled in Identity Inspector.</p>
  
  <p>It was working before, but know it has stopped. 
  "Auto" or "CounterPart" modes are still woking for other files except StoryBoard.</p>
  
  <p>A few days ago, I tried to update from Xcode 5 to 6, but later on gave up.
  Would that have something to do with it?</p>