Bug: Minimum quantity check disappears

Hi,

Opencart Version 2.0.1.1.

Note that I have created a product with a required option field. The minimum amount to order is set to 5.
Open the following link to the product: http://dev.preskop.be/index.php?route=p ... =Product+A

Steps to reproduce:
1. Open the link and verify the message "Het minimum te bestellen aantal is 5" (Saying the minimum quantity to order is 5)
2. Click the "Bestellen" (Order) button without filling in the required field.
3. Note that the message "Het minimum te bestellen aantal is 5" and the minimum amount check disappears. You are now able to add less than 5 (the minimum) amounts to the cart.

Although the check still happens in the shopping cart, there is no need to let the "minimum amount check" disappears.

Kind regards,

Koen