title: antd SubMenu "TypeError: Cannot read property 'isRootMenu' of undefined"
body: <p>I use antd 3.15 and GraphQL to fetch data and generate a list of SubMenu and Menu.Item inside of Menu. However, I got the error message like this <code>Uncaught TypeError: Cannot read property 'isRootMenu' of undefined</code> I have no idea what is wrong with my code. <code>isRootMenu</code> is not a prop listed anywhere on the doc. <a href="http://ant.design/components/menu/#header" rel="nofollow noreferrer">ant.design/components/menu/#header</a> and when I hardcoded all the SubMenu and Menu.List there is no problem. Can I iterate data from GraphQL to generate the  SubMenu and Menu.List?</p>
  
  <p>Can someone help me with this issue, please? Thank you! Here is my code:</p>
  
  <pre><code>import * as React from 'react';
  import './SideNav.scss';
  import { Menu, Icon } from 'antd';
  import gql from 'graphql-tag';
  import { Query } from 'react-apollo';
  
  const FLOORS_QUERY = gql`
    query {
      getAllFloors {
        id
        floorName
        rooms {
          id
          roomName
          roomNumber
          roomDescription
        }
      }
    }
  `;
  
  export default class SideNav extends React.Component {
    render() {
      return (
        &lt;Menu theme="light" defaultSelectedKeys={['1']} mode="inline"&gt;
          &lt;Query query={FLOORS_QUERY}&gt;
            {({ loading, error, data }) =&gt; {
              if (loading) return &lt;h4&gt; loading... &lt;/h4&gt;;
              if (error) console.log(error);
              console.log(data);
              return (
                &lt;React.Fragment&gt;
                  {data.getAllFloors.map((floor) =&gt; (
                    &lt;SubMenu
                      key={floor.id}
                      title={
                        &lt;span&gt;
                          &lt;Icon type="plus" /&gt;
                          &lt;span&gt;{floor.floorName}&lt;/span&gt;
                        &lt;/span&gt;
                      }
                    &gt;
                      &lt;React.Fragment&gt;
                        {floor.rooms.map((room) =&gt; (
                          &lt;Menu.Item key={room.id}&gt;{room.roomNumber}&lt;/Menu.Item&gt;
                        ))}
                      &lt;/React.Fragment&gt;
                    &lt;/SubMenu&gt;
                  ))}
                &lt;/React.Fragment&gt;
              );
            }}
          &lt;/Query&gt;
        &lt;/Menu&gt;
      );
    }
  }
  </code></pre>