fix mailer exceptions when registrant signs up for volunteering
fix mailer exceptions when registrant signs up for volunteering

rdunlop/unicycling-registration,scotthue/unicycling-registration,rdunlop/unicycling-registration,rdunlop/unicycling-registration,scotthue/unicycling-registration,scotthue/unicycling-registration,rdunlop/unicycling-registration