Deleted virtual project prevents creation of new project with the same name

Hi,

This was my first time to try to create a MapRoulette challenge. As I was unfamiliar with the interface and options, I initially create a Project with the "Virtual" setting, assuming I would be able to add new challenges to that as well.

Turns out you can only add existing challenges to a virtual project, not new ones. That by itself is not an issue (although I would recommend to document this more clearly on the options tooltip), but when I subsequently deleted the virtual project, and attempted to create a new project with exactly the same name, I received the error below about a unique constraint being violated.

Clearly, deleting the project does not remove the reference to it in some table, causing this issue. I guess this may be a safeguard for virtual projects referencing the same project name. However, when there are no references, as in my case with an entirely new unused project, it should be possible to definitively delete a project.

No files or tests are named. Reproduce the sequence of creating a virtual project, deleting it, and creating another project with the same name, then trace the project deletion path and the unique-constraint error. Done means an unused deleted project no longer prevents reuse of its name, with coverage for this sequence.