Modify Account class to handle NULL references This patch modifies the Account class to defer to using the associated domain's tid/ssid/qid fields if the per-instance fields are None/NULL.

Modify SQL update script to accept NULL fields for users The value NULL in the qid/ssid/tid fields of the user table means that the value from the associated domain record should be used instead. This patch modifies the PL/pgSQL functions used by Dovecot and Postfix accordingly.