Followup r78117: information was still leaked through the caption of the Edit tab...

Followup r78117: information was still leaked through the caption of the Edit tab (which is "Create" for nonexistent pages) for users who had edit but not read rights. This may seem like a ridiculous case, but since we automatically disallow edit if you can't read, it's easy to forget to disallow editing as well as reading. Fixed this by not showing the edit tab at all if the user can't read (which makes sense since it's also hidden if the user is explicitly forbidden from editing).