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)

expect(updateCount).toBe(1);
  });
  it('should update children even if parent blocks updates', function() {
    var parentRenderCount = 0;
    var childRenderCount = 0;
    var Parent = React.createClass({
      shouldComponentUpdate: function() {
        return false;
      },
      render: function() {
        parentRenderCount++;
        return <Child ref="child" />;
      },
    });
    var Child = React.createClass({
      render: function() {
        childRenderCount++;
        return <div />;
      },
    });
    expect(parentRenderCount).toBe(0);
    expect(childRenderCount).toBe(0);
    var instance = <Parent />;
    instance = ReactTestUtils.renderIntoDocument(instance);
    expect(parentRenderCount).toBe(1);
    expect(childRenderCount).toBe(1);
    ReactUpdates.batchedUpdates(function() {
      instance.setState({x: 1});
    });
    expect(parentRenderCount).toBe(1);