Identify groups without any users

I am attempting to identify, in 9r1, groups which do not contain any users. I have identified multiple situations where this happens and the group is empty via the GUI. But the below query in Inspector is returning no rows anytime I set the HAVING line to 0. Having 1 will show me all the groups which have 1 user.

SELECT UniqueName, count("Users".UniqueName) FROM ariba.user.core.Group GROUP BY UniqueName HAVING count("Users".UniqueName) = 0

Is this some sort of null handling issue?