PostgreSQL: Fix Special:ActiveUsers GROUP BY query
For GROUP BY queries, PostgreSQL require all columns in the
unaggregated part of the select list to also be in the
GROUP BY list.
To fix this, add user_name and user_id to the GROUP BY list along side
This addition cannot change the query results, because user_name and
user_id are functionally dependent on qcc_title: user_name because
of the WHERE clause for this query, and user_id due to the 1 to 1
relationship between user_name and user_id enforced by their unique
and not null constraints on the underlying table.
This has been tested on PostgreSQL and MySQL.