When completing a Return, if the Return Total is negative, Exchange payment gets credit amount

Description

Precondition: using the Quicksilver default promotion

Steps to reproduce:

1. Go to the QuickSilver sample site
2. Place an order with 2 shipments:
   • Shipment 1: SKU-44477844 (price $52.5) quantity is 1
   • Shipment 2: SKU-44477844 (price $52.5) quantity is 11
     => off 20% men shoes and $50 order discount is applied
3. Go to Commerce Manager.
4. Complete the first shipment.
5. Create a return => 20% off mens' shoes and $50 off order is invalidated. The return total is negative -$8.
6. Create an exchange, then complete the return.

Expected:

• Return information remains.
• No exchange payment or an exchange payment of $0.

Actual:

• Return information is updated.
• The exchange payment has credit amount.

Note:

• In Commerce 12, if an order has only 1 shipment, we cannot create return due to COM-6340. If an order has 2 shipments, the Return is created successfully, then the issue happens after creating the exchange and completing the return.
• In Commerce 11.5.0, the issue also happens with a single shipment order.