metabrainz/musicbrainz-server — pull request #82 by mwiencek (2013-02-03 17:26:03+00:00)
Title: MBS-5719: Track number sometimes missing in rel editor

If a relationship whose target is a recording that's also part of the
tracklist is parsed before the recording node for the actual tracklist
is parsed, then the recording Entity will be missing its number
attribute, among other things.

http://tickets.musicbrainz.org/browse/MBS-5719

Manual testing, QUnit tests still pass.