Positive commission for credit notes

[arielbarreiros96]

Module

sale_commission_product_criteria

Describe the bug

When Product Criteria is used as commission type, the settlement of credit notes may create commissions with positive amount.

To Reproduce

Affected versions: at least 14.0 and 16.0

Steps to reproduce the behavior:

1. Create a Commission Type, and under type select Product Criteria
2. Under rules, create a Rule that applies for a Product Category or Product
3. Create a invoice with an agent that use that particular commission type and a product that meets the previously created rule.
4. Add a credit note to the very same invoice
5. Create a settlement for the agent involved (you may have to register payment, check on Commission Type invoice status)

Expected behavior The settlement should contain a line of commission with a positive amount, related to the invoice. The settlement should contain another line with the same amount, but in this case, as a negative amount, related to the credit note. In reality, there are 2 positive lines with the same amount.

Additional context Tested on v14 CE and v16 CE