While editing http://test.musicbrainz.org/release/d9207330-8a89-302a-9d7b-05b85015b896/edit I got:

Caught exception in MusicBrainz::Server::Controller::ReleaseEditor::Edit->edit "Failed query:
'INSERT INTO edit_label (edit, label) VALUES (?, ?)'
(13523170 )
DBD::Pg::st execute failed: ERROR: null value in column "label" violates not-null constraint at /home/mbserver/musicbrainz/mb_server-next/script/../lib/Sql.pm line 102.

at /home/mbserver/musicbrainz/mb_server-next/script/../lib/MusicBrainz/Server/Data/Edit.pm line 281
at /home/mbserver/musicbrainz/mb_server-next/script/../lib/MusicBrainz/Server/Data/Edit.pm line 287
...propagated at /home/mbserver/musicbrainz/mb_server-next/script/../lib/MusicBrainz/Server/ControllerBase/ReleaseEditor.pm line 155."