Protection against creating a page with the same name ignores empty pages

Steps to reproduce:

• create a page, called IT Division
• save the newly created page, without filling in any content
• go back in the same context as before
• create another page, called IT Division (again)

Expected result:

• the error message saying that the page exists should be displayed on the create form, and creation should not proceed

Actual result:

• the creation proceeds, the editor for the new page is displayed