when changing the order, COD payment is deleted

[fabiocostanza]

Describe the bug
Hello,
congratulations for the module, I am having a problem with the Prestashop 1.7.6.x version when I modify the order, the cash on delivery is eliminated.
Can you fix this problem?
thank you very much

Prestashop version(s)
Prestashop 1.7.6.x

To Reproduce
Steps to reproduce the behavior:

1. Go to 'Admin > Orders'
2. Click on ' VIEW'
3. Scroll down to 'Customer Details'
4. When i edit, the payment reference (COD) is lost