Proximity search query broken when searching within smart groups

(this also affects v4.1.beta3)

When executing a proximity search within a group, the query includes "AND cgc.group_id = 34" (where 34 is the group ID). If the group is a smart group, this query will fail as the civicrm_group_contact table may have none or only part of the set of smart group contacts. (See also: http://forum.civicrm.org/index.php/topic,23398.msg98273.html)

A non-optimal solution is simply to disallow the inclusion of smart groups in proximity searches, but this may be preferable to returning incomplete results.