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)

var A = React.createClass({
      getInitialState: function() {
        return {x: this.props.x};
      },
      componentWillReceiveProps: function(nextProps) {
        var newX = nextProps.x;
        this.setState({x: newX}, function() {
          
          expect(this.state.x).toBe(newX);
          callbackCount++;
        });
      },
      render: function() {
        return <div>{this.state.x}</div>;
      },
    });
    var container = document.createElement('div');
    ReactDOM.render(<A x={1} />, container);
    ReactDOM.render(<A x={2} />, container);
    expect(callbackCount).toBe(1);
  });
  it('calls asap callbacks properly', function() {
    var callbackCount = 0;
    var A = React.createClass({
      render: function() {
        return <div />;
      },
      componentDidUpdate: function() {
        ReactUpdates.asap(function() {
          expect(this).toBe(component);