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

@@ -2,16 +2,17 @@ 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
-    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:]):
-  if delivery_dict[previous_brain.delivery_uid].getDestination() != delivery_dict[next_brain.delivery_uid].getSource():
-    portal.restrictedTraverse(active_process).postResult(
-     ActiveResult(summary=script.getId(),
-         detail='%s has tracking error' % context.getRelativeUrl(),
-         result='',
-         severity=100))
+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:]):
+    if delivery_dict[previous_brain.delivery_uid].getDestination() != delivery_dict[next_brain.delivery_uid].getSource():
+      portal.restrictedTraverse(active_process).postResult(
+       ActiveResult(summary=script.getId(),
+           detail='%s has tracking error' % context.getRelativeUrl(),
+           result='',
+           severity=100))