Crash when changing conditions in edit search

To reproduce:

1. Open http://musicbrainz.org/search/edits
2. Select "Type" "is" "Add medium"
3. Click "Search"
4. Change the condition without removing it (so don't click the red X), I use "Artist" "is" "Cycles".

This results in "Internal Server Error" on production.

On test.musicbrainz.org I get the following exception:

Caught exception in MusicBrainz::Server::Controller::Edit->search "Failed query:
'SELECT edit.* FROM edit WHERE () LIMIT 500 OFFSET ?'
(0)
DBD::Pg::st execute failed: ERROR: syntax error at or near ")"
LINE 1: SELECT edit.* FROM edit WHERE () LIMIT 500 OFFSET '0'
^ at /home/musicbrainz/musicbrainz-server/script/../lib/Sql.pm line 79.