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)

}
    }
    if (__DEV__) {
      
      if (renderedComponent === undefined &&
          inst.render._isMockFunction) {
        
        
        renderedComponent = null;
      }
    }
    return renderedComponent;
  },
  /**
   * @private
   */
  _renderValidatedComponent: function() {
    var renderedComponent;
    ReactCurrentOwner.current = this;
    try {
      renderedComponent =
        this._renderValidatedComponentWithoutOwnerOrContext();
    } finally {
      ReactCurrentOwner.current = null;
    }
    invariant(
      
      renderedComponent === null || renderedComponent === false ||
      ReactElement.isValidElement(renderedComponent),
      '%s.render(): A valid React element (or null) must be returned. You may have ' +