surveys and surveys statistics reports are not seems to working.

Tools > Reporting > Surveys > Surveys and surveys statistics

Client Traceback (most recent call last):
  File "/home/han/rdtool/client-web/trunk/addons/web/common/dispatch.py", line 161, in dispatch
    response["result"] = method(controller, self, **self.params)
  File "/home/han/rdtool/client-web/trunk/addons/web/controllers/main.py", line 940, in load
    return self.fields_view_get(req, model, view_id, view_type, toolbar=toolbar)
  File "/home/han/rdtool/client-web/trunk/addons/web/controllers/main.py", line 797, in fields_view_get
    fvg = Model.fields_view_get(view_id, view_type, context, toolbar, submenu)
  File "/home/han/rdtool/client-web/trunk/addons/web/common/openerplib/main.py", line 373, in proxy
    *args)
  File "/home/han/rdtool/client-web/trunk/addons/web/common/openerplib/main.py", line 250, in proxy
    result = self.connector.send(self.service_name, method, *args)
  File "/home/han/rdtool/client-web/trunk/addons/web/common/openerplib/main.py", line 102, in send
    return getattr(service, method)(*args)
  File "/usr/lib/python2.6/xmlrpclib.py", line 1199, in __call__
    return self.__send(self.__name, args)
  File "/usr/lib/python2.6/xmlrpclib.py", line 1489, in __request
    verbose=self.__verbose
  File "/usr/lib/python2.6/xmlrpclib.py", line 1253, in request
    return self._parse_response(h.getfile(), sock)
  File "/usr/lib/python2.6/xmlrpclib.py", line 1392, in _parse_response
    return u.close()
  File "/usr/lib/python2.6/xmlrpclib.py", line 838, in close
    raise Fault(**self._stack[0])

Server Traceback (most recent call last):
  File "/home/han/rdtool/server/trunk/openerp/wsgi.py", line 72, in xmlrpc_return
    response = xmlrpclib.dumps((result,), methodresponse=1, allow_none=False, encoding=None)
  File "/usr/lib/python2.6/xmlrpclib.py", line 1132, in dumps
    data = m.dumps(params)
  File "/usr/lib/python2.6/xmlrpclib.py", line 677, in dumps
    dump(v, write)
  File "/usr/lib/python2.6/xmlrpclib.py", line 699, in __dump
    f(self, value, write)
  File "/usr/lib/python2.6/xmlrpclib.py", line 780, in dump_struct
    dump(v, write)
  File "/usr/lib/python2.6/xmlrpclib.py", line 699, in __dump
    f(self, value, write)
  File "/usr/lib/python2.6/xmlrpclib.py", line 780, in dump_struct
    dump(v, write)
  File "/usr/lib/python2.6/xmlrpclib.py", line 699, in __dump
    f(self, value, write)
  File "/usr/lib/python2.6/xmlrpclib.py", line 780, in dump_struct
    dump(v, write)
  File "/usr/lib/python2.6/xmlrpclib.py", line 699, in __dump
    f(self, value, write)
  File "/usr/lib/python2.6/xmlrpclib.py", line 759, in dump_array
    dump(v, write)
  File "/usr/lib/python2.6/xmlrpclib.py", line 699, in __dump
    f(self, value, write)
  File "/usr/lib/python2.6/xmlrpclib.py", line 703, in dump_nil
    raise TypeError, "cannot marshal None unless allow_none is enabled"
TypeError: cannot marshal None unless allow_none is enabled