Creating un-deletable folder with no visible documents in it

1. Create a new folder in the cms
2. Add a document (type news) to this new folder (don't save it! don't change anything in it)
3. Close that document and Discard changes
4. Try to delete the folder

Dialog 'The folder test2 is not empty and therefore cannot be deleted.'

Expected result: Being able to delete the folder.

It doesn't seem to happen with all of the documenttypes.