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)

'returned undefined, an array or some other invalid object.',
      this.getName() || 'ReactCompositeComponent'
    );
    return renderedComponent;
  },
  /**
   * Lazily allocates the refs object and stores `component` as `ref`.
   *
   * @param {string} ref Reference name.
   * @param {component} component Component to store as `ref`.
   * @final
   * @private
   */
  attachRef: function(ref, component) {
    var inst = this.getPublicInstance();
    invariant(inst != null, 'Stateless function components cannot have refs.');
    var publicComponentInstance = component.getPublicInstance();
    if (__DEV__) {
      var componentName = component && component.getName ?
        component.getName() : 'a component';
      warning(publicComponentInstance != null,
        'Stateless function components cannot be given refs ' +
        '(See ref "%s" in %s created by %s). ' +
        'Attempts to access this ref will fail.',
        ref,
        componentName,
        this.getName()
      );
    }
    var refs = inst.refs === emptyObject ? (inst.refs = {}) : inst.refs;