function rsvp_function_load_guests creating invalid SQL for PostgreSQL

In the file rsvp.functions.inc, function rsvp_function_load_guests, lines 403 & 406 the queries being generated don't work with PostgreSQL (version 8.4.1). The query being generated is (one example):

SELECT SUM(totalguests) 
FROM rsvp r LEFT JOIN rsvp_invite u ON r.rid = u.rid 
            LEFT JOIN users us ON u.uid = us.uid 
	            LEFT JOIN rsvp_realname n ON u.email = n.email  
WHERE u.rid = 1 AND u.response='none' 
ORDER BY u.email

PostgreSQL chokes on the 'ORDER BY' clause with the error:

Query failed: ERROR: column "u.email" must appear in the GROUP BY clause or be used in an aggregate function

This is because in the context of a single, global aggregate of all results the order by is contradictory. If you're going to sort by email, you need to have some distinction by email or what is the purpose of the sort, right?