metabrainz/musicbrainz-server — pull request #44 by ocharles (2013-01-25 17:12:46+00:00)
Title: MBS-5655: Discard release labels in the RE if they have no data

If a release label is added that has no label nor catalog number, then this
release label is deemed as 'empty' and is either discarded (when adding a new
release label), or counts as a deletion (if there was previously a release
label).