Bug 12426: [QA Follow-up] Clear to_address to force update

 Bug 12426: [QA Follow-up] Clear to_address to force update

When resending an email from the Notices tab in Patrons, we would like
to use the recent email address.

Test plan:
[1] Look up a patron with some notices sent.
[2] Adjust the patron email address (watch AutoEmailPrimaryAddress).
[3] Resend the notice. Verify if the new address was used.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>