erp5_core: remain zero

product/ERP5/bootstrap/erp5_core/DocumentTemplateItem/portal_components/document.erp5.Movement.py

@@ -417,7 +417,7 @@ class Movement(XMLObject, Amount, CompositionMixin, AmountGeneratorMixin):
     quantity = self.getQuantity()
     if quantity :
       source_asset_price = self.getSourceAssetPrice()
-      if source_asset_price :
+      if source_asset_price is not None:
         return source_asset_price * - quantity
     return None
 
@@ -461,7 +461,7 @@ class Movement(XMLObject, Amount, CompositionMixin, AmountGeneratorMixin):
     quantity = self.getQuantity()
     if quantity :
       destination_asset_price = self.getDestinationAssetPrice()
-      if destination_asset_price :
+      if destination_asset_price is not None:
         return destination_asset_price * quantity
     return None