Describe the bug

In the BO > Order page > Order detail page > we have already a gifted_product in the order.
When we add a Product with an associated gift, The gifted product quantity is not updated

Expected behavior

Explain what you expected to happen instead.

Steps to Reproduce

Steps to reproduce the behavior:

1. Create a cart rule
   1.1. no code
   1.2. no condition
   1.3. Free gift demo_12
2. Go to BO > Orders > An old order created
3. add demo_12
4. See error: the quantity of the product added = 1 => it should be 2 (the discount is applied)
   

1.7.6.8 => ok

Additional information

• PrestaShop version: 1770rc1build2
• PHP version: 7.2