Sort names being returned incorrectly for multiple artist credits on /ws/1

From http://forums.musicbrainz.org/viewtopic.php?id=2766

Compare
http://musicbrainz.org/ws/1/release/e0630cf7-2e13-48c6-852a-47045cc80a96?type=xml&inc=tracks+puids+artist+release-events+labels+isrcs+artist-rels+release-rels+url-rels+track-rels+track-level-rels

and

http://classic.musicbrainz.org/ws/1/release/e0630cf7-2e13-48c6-852a-47045cc80a96?type=xml&inc=tracks+puids+artist+release-events+labels+isrcs+artist-rels+release-rels+url-rels+track-rels+track-level-rels

Both artists making up the credit have sort names, so I think this should be able to work?

http://musicbrainz.org/release/e0630cf7-2e13-48c6-852a-47045cc80a96

This is currently breaking the "Translate foreign artist names to English..." feature in Picard.

(Working fine for single-artist credits: http://musicbrainz.org/ws/1/release/9a2e98c7-03b0-496b-b3b1-1db0990a3e29?type=xml&inc=tracks+puids+artist+release-events+labels+isrcs+artist-rels+release-rels+url-rels+track-rels+track-level-rels )