[FIX] fleet: fix _get_default_state method
[FIX] fleet: fix _get_default_state method

If fleet.vehicle_state_active is not found in the system then the method
will raise an error, hence it won't allow creating any fleet.vehicle

closes odoo/odoo#30925
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo