BUG: Edit from Page menu in on a published page does not create a new draft

[fsbraun]

Steps to reproduce

• Create a draft page
• Publish
• Select "Edit..." from "Page" menu

BUG:

• The published page is still visible, but the toolbar shows a "Publish" button
• The structure board opens, and the user can is offered plugins to add (though adding fails due to the publish page's write protection)