Do not copy asset lot when copying sale subscription line

Closes #13785
(grafted from 4926ea6614fabc74223b4debe0c7ed92c5e70c1f)

--HG--
branch : 7.0

modules/sale_subscription_asset/sale.py

@@ -111,7 +111,7 @@ class SubscriptionLine(metaclass=PoolMeta):
             default = {}
         else:
             default = default.copy()
-        default.setdefault('lot')
+        default.setdefault('asset_lot')
         return super(SubscriptionLine, cls).copy(lines, default)
 
     @classmethod