editing non-og2list group causes error "The chosen address is already in use by another group", even when recipient blank

This error began appearing on a production site with lots of groups. It was caused by a row of bad data that ended up in og2list_groups, with nid=0 and a blank recipient.

deleting this row of bad data with "DELETE FROM og2list_groups WHERE nid = 0;" solves the problem and users were able to edit and save non-og2list groups again.

Checking this in the code, there are only two spots where a row can be inserted into og2list_groups - on new group creation in og2list_nodeapi() $op='insert', and on a group update where a mailing list is being set, in og2list_nodeapi() $op='update'.

The 'insert' op already has a check for $node->nid existing before it can run its insert statement:

But the 'update' op does not check for $node-nid != 0 before its insert:

I am still un-sure of quite how Drupal managed to pass the $node->recipient and run the query and end up with a blank recipient in the DB, but in any case it should never be inserting with nid=0.

The attached patch just adds a check for $node->nid in the update branch as well, to (hopefully) prevent these rows from going in. This fix is live on my og2list-after.postcarbon.org test site, and I have tested it by creating a new non-og2list group, editing that group, then editing it again and setting the recipient to make an og2list_groups row, then editing it a final time with that recipient. That should have tested all the logic in 'insert' and 'update' branches of og2list_nodeapi().

If anyone has an install they can apply and test on too, they could then mark this reviewed and tested by the community. Or I can create you a group on og2list-after to test on, just contact me directly.