As getBody always returns empty string by default.

edit(body=None) will try to update the _body attribute and fails.
Force conversion from None to empty string to authorise edit of Python Script documents
without content in my_body field.


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@42296 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/PythonScript.py

@@ -96,6 +96,8 @@ class PythonScript(XMLObject, ZopePythonScript):
       """
       override to call ZopePythonScript methods to initialize code
       """
+      if value is None:
+        value = ''
       self.write(value)
 
     def _setParameterSignature(self, value):