E.g., https://beta.musicbrainz.org/recording/create?edit-recording.name=Let%27s+Play+Fallout+New+Vegas+%28Modded%29+%3A+%2340&edit-recording.video=1&edit-recording.length=56%3A50&edit-recording.edit_note=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3Dc5LFv1P0ejY&edit-recording.artist_credit.names.0.artist.name=Gopher&edit-recording.url.0.link_type_id=74&edit-recording.url.0.text=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3Dc5LFv1P0ejY will create an arbitrary (but content-less) generic AR, but not include an URL relationship.
Not fixed by MBS-7549
Note that link_type_id 74 is a release-url relationship, not recording-url, which is why it breaks. Using the correct link type (or removing it and letting the URLCleanup guess it) works. But I'll make sure the code ignores bad link types and doesn't break the UI.