Do not try to validate empty TALES expression

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@43556 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/bootstrap/erp5_core/SkinTemplateItem/portal_skins/erp5_core/Base_validateStringFieldWithTALESExpression.xml

@@ -52,7 +52,8 @@
             <key> <string>_body</string> </key>
             <value> <string>from Products.ERP5Type.Utils import isValidTALESExpression\n
 from Products.Formulator.Errors import ValidationError\n
-\n
+if not value:\n
+  return True\n
 valid, message = isValidTALESExpression(value)\n
 if valid:\n
   return True\n

product/ERP5/bootstrap/erp5_core/bt/revision

-40899
+40900
\ No newline at end of file