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)

getInitialState: function() {
        return {x: 0};
      },
      shouldComponentUpdate: function() {
        shouldUpdateCount++;
      },
      componentDidUpdate: function() {
        updateCount++;
      },
      render: function() {
        return <div>{this.state.x}</div>;
      },
    });
    var instance = ReactTestUtils.renderIntoDocument(<Component />);
    expect(instance.state.x).toBe(0);
    var callbacksRun = 0;
    ReactUpdates.batchedUpdates(function() {
      instance.setState({x: 1}, function() {
        callbacksRun++;
      });
      instance.forceUpdate(function() {
        callbacksRun++;
      });
      expect(instance.state.x).toBe(0);
      expect(updateCount).toBe(0);
    });
    expect(callbacksRun).toBe(2);
    
    expect(shouldUpdateCount).toBe(0);
    expect(instance.state.x).toBe(1);