administration: fix catalog table scan in Item_checkTrackingList

This fix a regression from 920655a2 : when item has no tracking, uid was
passed an empty list and this fetched all catalog.
Also call getObject explicitly only once instead of having it called
implicitly twice.

bt5/erp5_administration/SkinTemplateItem/portal_skins/erp5_administration/Item_checkTrackingList.py

@@ -2,13 +2,14 @@ from Products.CMFActivity.ActiveResult import ActiveResult
 portal = context.getPortalObject()
 
 tracking_list = list(reversed(portal.portal_simulation.getCurrentTrackingList(aggregate_uid=context.getUid())))
-delivery_dict = {
-    x.uid: x
+if tracking_list:
+  delivery_dict = {
+      x.uid: x.getObject()
       for x in portal.portal_catalog(
           uid=[x.delivery_uid for x in tracking_list],
       )
-}
-for previous_brain, next_brain in zip(tracking_list, tracking_list[1:]):
+  }
+  for previous_brain, next_brain in zip(tracking_list, tracking_list[1:]):
     if delivery_dict[previous_brain.delivery_uid].getDestination() != delivery_dict[next_brain.delivery_uid].getSource():
       portal.restrictedTraverse(active_process).postResult(
        ActiveResult(summary=script.getId(),