SQL-warning Unknown column 'ifu.nameISNULL01DESCu.name'

While sorting the invitation details list by users, I get the following error:

user warning: Unknown column 'ifu.nameISNULL01DESCu.name' in 'order clause' query: SELECT i.email, i.invitee AS uid, u.name, i.created, i.expiry, i.joined, i.canceled FROM invite i LEFT JOIN users u ON u.uid = i.invitee AND u.uid <> 0 WHERE i.uid = 1 ORDER BY ifu.nameISNULL01DESCu.name ASC LIMIT 0, 50 in modules/invite/invite_admin.inc on line 288.

It seems that the field value in the table header definition gets malformed:

    array('data' => t('Username'), 'field' => 'if(u.name IS NULL, 0, 1) DESC, u.name'),

I'm not sure what the expression is for, but a simple

    array('data' => t('Username'), 'field' => 'u.name'),

does the job. At least with mysql.