Not sure if this will do the trick or not but....

Log into your site as admin, go under configuration and then product listing, choose display product model and change the 1 to a 0. Then stick out your tongue at a 33 1/3 degree angle, hop on your left foot twice and then spin four times counter-clockwise, then click on update.

Try that in all your transactions (from start to invoice) and if that does not do it, I am sure someone else will post back.

Good luck and may the force be with you

Sincerely,

0be1