title: Xcode menu item Editor / Add Model Version... missing
body: <p>Every once in a while I try to add a new data model version, and the menu item is missing.  It seems the Editor menu is supposed to change depending on the file selected, and this sometimes doesn't happen.  It the past I've randomly clicked, cleaned, built, etc. and eventually it showed up again with me not knowing what happened.  Today it seems restarting Xcode fixed it, but I don't know if that will always work.  Below are two screen shots, the first showing the wrong menu, and the second showing the correct menu.  My data model is selected in both cases.  Has anyone else seen this?  Is it a bug, or is there some setting or selection I'm missing?
  <img src="https://i.stack.imgur.com/ydraJ.png" alt="enter image description here">
  <img src="https://i.stack.imgur.com/zO7GJ.png" alt="enter image description here"></p>