Commerce: No warning when adding existing catalog to project

Description

This issue also happens with Quick Silver & Seagull sample sites.
Steps to reproduce

1. Create a project named ProjectA.
2. Select a catalog.
3. Add it to ProjectA via the 'Add to Translation Project' context menu option.
4. Repeat step 3.
5. There is no message to inform you that the current catalog already exists in the selected project. It works fine with CMS.