check if there is no line with an empty resource

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@4978 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/Inventory.py

@@ -81,6 +81,7 @@ class Inventory(Delivery):
       node = self.getDestination()
       for movement in self.getMovementList():
         resource =  movement.getResourceValue()
+        if resource is not None:
           variation_text = movement.getVariationText()
           if (resource,variation_text) not in resource_and_variation_list:
             resource_and_variation_list.append((resource,variation_text))