Empty directories are sometimes left behind

This issue was automatically migrated from Google Code.
_Original author: carl@contraflo.ws (October 07, 2012 05:33:16)_
_Original issue: https://github.com/google-code-export/beets/issues/445_

The report only describes empty directories being left behind and provides no file, command, reproduction steps, or test reference. Start by locating the code that moves or removes library files, then reproduce the behavior and add coverage showing that directories are cleaned up when they become empty.

Written by the indexing model from the issue text.