Don't display the drop zone when user doesn't have edit rights

If a document has no file in it, a drop zone is usually displayed to show how/where to add a content quickly by drag and drop.

But if the user has no edit rights the drop zone shouldn't be displayed.
Currently a browser message inform the user that he has not the rights to do it but we should only display an small sentence saying "no main file"
-> just informative, no call to action that you cannot perform (negative feeling).