When I select an artist to use in a relationship and then click on Relate artist to recordings, the process can't be ended.

Current result
1. Select an artist to use in a relationship: e.g. John Eliot Gardiner (http://musicbrainz.org/artist/eb4fb6c3-f8e5-4923-aea9-436fcf3cf2c0)
2. Go to a release: e.g. Così fan tutte (http://musicbrainz.org/release/3f08f1c8-94ee-4328-beb8-b66a2fe8f893)
3. Click on Relate John Eliot Gardiner to recordings
4. Select the type of relation: e.g. conducted.
5. Put a comment: e.g. a link http://www.deutschegrammophon.com/cat/single?sort=newest_rec&PRODUCT_NR=4378292&SearchString=cosi+fan+tutte&UNBUYABLE=1&per_page=50&flow_per_page=50&presentation=flow
6. Click Enter edits
7. Bang: You receive the following message

Internal Server Error
Oops, something went wrong!
Error message: (No details about this error are available)
We're terribly sorry for this problem. Please wait a few minutes and repeat your request — the problem may go away.

Expected result:
Steps 1 to 6 works as for now
Step 7 doesn't give any error.