Steps:

1. Go to Admin/Content Types
2. Create new Content Type Group
3. Click button to add new Content Type
4. When creating form of new CT is opened click Content Types using breadcrumbs (do not save)
5. Mark checkbox next to CT group from step 2 as checked
6. Click Trash button and then Delete

Actual result:

Error message is shown:
Argument '$contentTypeGroup' is invalid: Content type group has content type instances User is unable to remove Content Type Group because of Content Type's draft

Expected result:

Content Type Group is removed.