I am receiving order forms without orders

We continue to get email notifications of orders without quantities on any of the products. The last 2 orders we received were submitted this way.  I have tried to recreate this by leaving the order form blank, completing my name, address, etc., then submitting the form. Each time I get an error message that I must fill in a quantity on at least one product. So how is it possible that we are receiving submissions with no quantities?  I am perplexed.

The form is here https://secure.jotformpro.com/form/41667029180960

Most likely, some people might have JavaScript disabled in their browsers, this causes some validations to get disabled. To solve this, please remove the current script of the form and replace it by the iFrame version