CSR UI: Cannot add promotion code if gift is out of stock

Description

Precondition:

• Promotion: Spend $10 and get a gift

Steps to reproduce:

1. Go to the CSR UI.
2. Add items to cart so that the number of gift is greater than the number in stock or the than max quantity setting => correct warning message displays.
3. Add any characters to the promotion code.

Expected:
Add promotion code successfully.

Actual:
Cannot add promotion code. There is message warning user "The gift as not enough quantity in stock and was removed from your cart."