[FIX] mrp: warning for lot
[FIX] mrp: warning for lot

The constraint should only check for move lots with a lot number already
filled in. Indeed, in case we use work orders, we can potentially create
move lots without S/N, and fill in the S/N later.

opw-727679

hip-odoo/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,hip-odoo/odoo,hip-odoo/odoo,ygol/odoo,hip-odoo/odoo,ygol/odoo,hip-odoo/odoo,hip-odoo/odoo