Fill unit price of purchase line created automatically

Since 2f25450e11f6 the on_change_product does not always set a unit price for
purchase line. But as the field is required, it must be filled for line
created.

modules/product_kit/purchase.py

@@ -1,5 +1,8 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
+
+from decimal import Decimal
+
 from trytond.i18n import gettext
 from trytond.model import ModelSQL, ModelView, fields
 from trytond.modules.product import round_price
@@ -59,7 +62,10 @@ class Line(order_line_mixin('purchase'), metaclass=PoolMeta):
     def get_component_order_line(self, component, **values):
         values = values.copy()
         values['purchase'] = self.purchase
-        return super().get_component_order_line(component, **values)
+        line = super().get_component_order_line(component, **values)
+        if line.unit_price is None:
+            line.unit_price = round_price(Decimal(0))
+        return line
 
     @classmethod
     def get_move_product_types(cls):

modules/product_kit/tests/scenario_product_kit_purchase.rst

@@ -259,7 +259,7 @@ Check unit price of moves::
     >>> shipment.reload()
     >>> invoice.reload()
     >>> sorted([m.unit_price for m in shipment.incoming_moves])
-    [Decimal('5.0000'), Decimal('5.0000'), Decimal('9.4545'), Decimal('14.1818')]
+    [Decimal('0.0000'), Decimal('5.0000'), Decimal('9.4545'), Decimal('14.1818')]
 
 Check backorder moves::
 

modules/production_outsourcing/production.py

@@ -1,5 +1,7 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
+
+from decimal import Decimal
 from itertools import groupby
 
 from trytond.i18n import gettext
@@ -215,6 +217,8 @@ class Production(metaclass=PoolMeta):
             factor * self.routing.supplier_quantity)
         line.purchase = purchase
         line.on_change_product()
+        if line.unit_price is None:
+            line.unit_price = round_price(Decimal(0))
         return line
 
     @classmethod