Folders appear empty but cannot be deleted due to old file revisions remaining

[dasgarner]

If a file has revisions and then is moved to a different folder, it is possible for the old revisions to remain in the original folder.
When this happens, the folder appears empty but is not. This stops the folder from being deleted.

Affects v3 also.

[dasgarner]

When we move a media item to a different folder, do we also move the old revisions? If not, then that might explain this behaviour.