from http://bugs.musicbrainz.org/ticket/4880

If you try to change options or close Picard (when it apparently autosaves the current config), and the ~/ drive is full, Picard ends up zeroing out it's config file. A better approach would seem to be to first check if there is room to store the new config file, rather than just assuming there is enough room, and ending up zeroing out the existing config file.