If a user has policy Content/Edit with Location limitation any his attempt on accessing Content in admin back office will result in 500 error:

InvalidArgumentException
Argument '$targets' is invalid: Must contain Location objects 

Steps to reproduce:
1. Clean installation of Ibexa DXP v3 or eZ Platform 2.5
2. Log in as admin user into the back office
3. Go to Roles -> Editor
4. Add content/edit policy to it. Set Location Limitation to top-level Location (/Ibexa Platform)
5. Create a new Editor user.
6. Log in to the back office as an Editor user.
7. Click on "Content Structure" tab.

Result:

InvalidArgumentException
Argument '$targets' is invalid: Must contain Location objects

Expected result:
Content is viewed normally.