Hello,

After updating to React 15.0.1, we are getting the following error:

```
Uncaught TypeError: Cannot read property 'addEventListener' of null
```

![image](https://cloud.githubusercontent.com/assets/4996164/14602577/5bb4e9f2-0571-11e6-9aa1-98de49f50d76.png)

return {x: 0};
      },
      componentWillMount: function() {
        a = this;
      },
      render: function() {
        return <div>A{this.state.x}</div>;
      },
    });
    var B = React.createClass({
      componentWillMount: function() {
        a.setState({x: 1});
      },
      render: function() {
        return <div />;
      },
    });
    ReactUpdates.batchedUpdates(function() {
      ReactTestUtils.renderIntoDocument(
        <div>
          <A />
          <B />
        </div>
      );
    });
    expect(a.state.x).toBe(1);
    expect(ReactDOM.findDOMNode(a).textContent).toBe('A1');
  });
  it('calls componentWillReceiveProps setState callback properly', function() {
    var callbackCount = 0;