update non-existing item with return_values "ALL_OLD" fails with 500

If you update non existing item with return_values "ALL_OLD" you will get 500 error

Server side:
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 144, in __call__
    return resp(environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/routes/middleware.py", line 131, in __call__
    response = self.app(environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 144, in __call__
    return resp(environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 130, in __call__
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 195, in call_func
    return self.func(req, *args, **kwargs)
  File "/opt/stack/magnetodb/magnetodb/common/wsgi.py", line 244, in __call__
    action_result = self.execute_action(action, request, **action_args)
  File "/opt/stack/magnetodb/magnetodb/common/wsgi.py", line 258, in execute_action
    return self.dispatch(self.controller, action, request, **action_args)
  File "/opt/stack/magnetodb/magnetodb/common/wsgi.py", line 267, in dispatch
    return method(*args, **kwargs)
  File "/opt/stack/magnetodb/magnetodb/api/__init__.py", line 35, in wrapper
    return f(self, *args, **kwargs)
  File "/opt/stack/magnetodb/magnetodb/common/probe.py", line 94, in wrapper
    return f(*args, **kwargs)
  File "/opt/stack/magnetodb/magnetodb/api/openstack/v1/data/update_item.py", line 94, in process_request
    parser.Parser.format_item_attributes(old_item)
  File "/opt/stack/magnetodb/magnetodb/api/openstack/v1/parser.py", line 419, in format_item_attributes
    for (attr_name, attr_value) in item_attributes.iteritems():
AttributeError: 'NoneType' object has no attribute 'iteritems