Fallback to 0 when price list is not setting price ratio of components

Closes #11947
(grafted from 3d7d5452040338cd6c9bec7fc3cde91c4e1f9585)

--HG--
branch : 6.0

modules/product_kit/common.py

@@ -281,7 +281,7 @@ def order_line_component_mixin(prefix):
             for component in components:
                 product = component.product
                 list_price = Uom.compute_price(
-                    product.default_uom, product.list_price,
+                    product.default_uom, product.list_price_used or 0,
                     component.unit)
                 if component.fixed:
                     list_price *= Decimal(str(component.quantity / quantity))