History's version field must be an empty string, not None.

See HistoryTests.checkSimpleHistory.

git-svn-id: https://svn.erp5.org/repos/neo/trunk@1792 71dcc9de-d417-0410-9af5-da40c76e7ee4

neo/client/app.py

@@ -938,7 +938,7 @@ class Application(object):
             self.local_var.txn_info.pop('id')
             self.local_var.txn_info.pop('oids')
             self.local_var.txn_info['tid'] = serial
-            self.local_var.txn_info['version'] = None
+            self.local_var.txn_info['version'] = ''
             self.local_var.txn_info['size'] = size
             if filter is None or filter(self.local_var.txn_info):
                 history_list.append(self.local_var.txn_info)