[FIX] delivery: delivery with carrier but not linked to so
[FIX] delivery: delivery with carrier but not linked to so

When a delivery with free_over=True was not linked to a SO, it raised
an error.

opw:1843829

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo