We would like a feature like this too.

Yesterday we ran into this exact issue. We created a course with a user, shared it and then deleted the user again.

This resulted in the now orphaned course was visible for the other users, but they didn't have permissions to delete the course again. Thus, when other users clicked the "Shared Courses" button, they saw a no-man's-course, which should just be deleted, but couldn't. Not even the Admin user could delete it.

We ended up going into the settings of the orphaned course and set it to NOT shared, which removed it from the shared courses-list, even though the course technically hasn't been deleted.

If there is a better way to get rid of orphaned courses, we are all ears :)