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)

*       - componentWillReceiveProps (only called if parent updated)
 *       - shouldComponentUpdate
 *         - componentWillUpdate
 *           - render
 *           - [children's constructors or receive props phases]
 *         - componentDidUpdate
 *
 *     - componentWillUnmount
 *     - [children's componentWillUnmount]
 *   - [children destroyed]
 * - (destroyed): The instance is now blank, released by React and ready for GC.
 *
 * -----------------------------------------------------------------------------
 */
/**
 * An incrementing ID assigned to each component when it is mounted. This is
 * used to enforce the order in which `ReactUpdates` updates dirty components.
 *
 * @private
 */
var nextMountID = 1;
/**
 * @lends {ReactCompositeComponent.prototype}
 */
var ReactCompositeComponentMixin = {
  /**
   * Base constructor for all composite component.
   *
   * @param {ReactElement} element
   * @final