Error invoicing contract, services in contract turn into products in the invoice

[joanahead]

Bug

When doing and invoice from a contract, if there are any services* created within the contract, they turn into products (instead of services) in the invoice, and so, services' dates cannot be edited in the invoice.

• If you use services from the products/services Dolibarr database it works well, but if you defined the service as text in the contract it fails when building the invioice and turns those "text" services into products.

Environment

• Version: 12.0.2
• OS: Centos 7
• Web server: Apache
• PHP: 7.2
• Database: MySQL/

Steps to reproduce the behavior

Create customer contract. Add service from scratch to the contract (do NOT use preexistent services from services/products Dolibarr database). Create invoice from the contract.
Then in the invoice the service turned into a product and you cannot edit the dates (begin, end) of the service as it is a product that has no dates.