Can add category with duplicate name to Root category

Description

Steps to reproduce

1. Install Alloy template site (CMS 11.5.2).
2. Build and run the site to make sure Alloy content is imported.
3. Add the attached code file into the solution and then build.

Expected:
Episerver should not allow a duplicate category name to be added to the database.

Actual:
Check tblCategory table. You see a duplicate category name.

If duplicate category names exist, pages using that category break, and the editor can neither open nor edit the page.