[FIX] base, website_sale: vietnam zip not required

Zip cannot be required if not in format address.
It will break ecommerce, because the customer cannot
validate the adress because zip code is not displayed but required.

Fix case in JS where field is not display to avoid traceback.

This commit closes #58950

closes odoo/odoo#60694

Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>