In Content Edit mode there is a BadStateException being thrown in case of nonpublished content when trying to remove the only existing draft. This content cannot be removed using ContentService::deleteVersion but with ContentService::deleteContent instead.

Another issue which is related to this is the redirection happening after deleting the draft - you can't redirect to the content after removing it, it should redirect to parent location instead. It isn't possible to resolve parent location from nonpublished content using LocationService, an improvement to the kernel is needed.