erp5_trade: disallow setting items on Order Line view when Product has variations

bt5/erp5_trade/SkinTemplateItem/portal_skins/erp5_trade/Movement_isAggregateItemListEnabled.py

-"""This script is an helper to replace complex TALES expression
-for Base_viewTradeFieldLibrary/my_view_mode_aggregate_title_list.enable
 """
-
-# If the resource accepts items, and the context is a movements (ie. not a line
-# already containing cells or line that has variations but not cells yet)
-if context.getResource() and context.getResourceValue().getAggregatedPortalTypeList()\
-   and context.isMovement()\
-   and (('Cell' in context.getPortalType()) or not context.getVariationCategoryList()):
-  return True
+This script is used to know if a Line or Cell can use Items.
+"""
 
 # If the movement already has an aggregate, display it.
 if context.getAggregate():
   return True
 
-# If there's not resource yet, we give a chance to set an item.
-if context.getResource() is None and context.getPortalItemTypeList():
+# If there is a resource and the context is a movement...
+if context.getResource() and context.isMovement():
+  resource = context.getResourceValue()
+  # ...then the resource must accept Items and not use variations
+  # (in this case, Items are to be set on cells).
+  if resource.getAggregatedPortalTypeList() and \
+      (('Cell' in context.getPortalType()) or not resource.getVariationBaseCategoryList()):
     return True
 
 return False