Return from getACLRoles when contactID is null

Return from getACLRoles when contactID is null

I've made this patch the least possible code wise to allow brain space to think about the query....

Basically the where is WHERE acl.entity_table='civicrm_acl_role'....

if contact_id is set it becomes AND acl.entity_table = 'civicrm_contact'

Which means that it would only ever return empty results

(once this is merged more cleanup can happen but I wanted to
make this change easy to think through)