Steps to reproduce:

1. Using Firefox, go to PlatformUI;

2. Go to "Content -> Content structure";

3. On the rightside menu, choose content type "Folder";

4. The rotating loading icon will spin indefinitely and no edit page will ever load.
No error will be output on the firebug Console nor on any logs that I could find;

Also not working for Article, Landing Page, Place, Poll, Product, Wiki Page, File, Image and Video.
Issue doesn't appear to happen on Chrome.