erp5_web: skip not needed query

bt5/erp5_web/SkinTemplateItem/portal_skins/erp5_web/WebSection_getDocumentValue.py

@@ -3,6 +3,11 @@
    fix acquisition issues within the _aq_dynamic
    lookup from WebSection class.
 """
+if not name:
+  # Catalog does not search empty reference.
+  # Skip the query in such case.
+  return None
+
 if portal is None:
   portal = context.getPortalObject()