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)

it('should share reconcile transaction across different roots', function() {
    var ReconcileTransaction = ReactUpdates.ReactReconcileTransaction;
    spyOn(ReconcileTransaction, 'getPooled').andCallThrough();
    var Component = React.createClass({
      render: function() {
        return <div>{this.props.text}</div>;
      },
    });
    var containerA = document.createElement('div');
    var containerB = document.createElement('div');
    
    ReactUpdates.batchedUpdates(function() {
      ReactDOM.render(<Component text="A1" />, containerA);
      ReactDOM.render(<Component text="B1" />, containerB);
    });
    expect(ReconcileTransaction.getPooled.calls.length).toBe(2);
    
    
    ReactUpdates.batchedUpdates(function() {
      ReactDOM.render(<Component text="A2" />, containerA);
      ReactDOM.render(<Component text="B2" />, containerB);
    });
    expect(ReconcileTransaction.getPooled.calls.length).toBe(3);
  });
  it('should queue mount-ready handlers across different roots', function() {
    
    
    
    var a;
    var b;