Error Message back-end when changing Group Type

If I change a Group (back-end admin) from Closed to Invite-Only, or the other way around, it seems to work but it throws this message:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ')' at line 1 SQL=UPDATE mydb_social_clusters SET `type` = '3' WHERE `id` IN ()

So (a) reporting the problem, and (b) asking if I should worry about what this error may have done to my site?

Thanks!