Users are NOT shown on User Grid in Admin if Expired from their Primary group

Came across the bug in User Grid (Admin) when users are
NOT shown on the list as soon as they expire from the their Primary
Group.

Here is Reproduction Recipe:

1. Register User as a Member on Front or Admin so his ONLY and Primary
group is "Members".

2. Make sure to define some Expiration date/time via Groups tab while
editing User in Admin Console.

3. Let user expire from his Primary Group and see if you can find it
in User Grid in Admin Console.

The problem is that tend to JOIN Users table with Groups with Primary
group condition which results in the error described above when
Primary group is not set so user is NOT the member on any Group.