If key is not available, return None.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@36327 20353a03-c40f-0410-a6d1-a30d3c3de9de

bt5/erp5_upgrader/SkinTemplateItem/portal_skins/erp5_upgrader/ERP5Site_getUpgraderSignature.xml

@@ -566,7 +566,7 @@ signature_dict = {\n
 }\n
 \n
 if item is not None:\n
-  return signature_dict.get(item)\n
+  return signature_dict.get(item, None)\n
 else:\n
   return signature_dict\n
 

bt5/erp5_upgrader/bt/revision

-527
\ No newline at end of file
+528
\ No newline at end of file