The code

``` javascript
class Comp extends React.Component {
  componentWillMount() {
    setTimeout(() => {
      this.setState({});
    });
  }

  render() {
    return <div onClick={() => {}} />;
  }
}

ReactDOMServer.renderToString(<Comp />);
```

produces errors:

> Warning: React can't find the root component node for data-reactid value `.0`. If you're seeing this message, it probably means that you've loaded two copies of React on the page. At this time, only a single copy of React can be loaded at a time.
> 
> Uncaught TypeError: Cannot read property 'firstChild' of undefined

But if I remove `onClick` handler the errors go away...

See demo: http://codepen.io/dened/pen/YyByYr

},
  /**
   * Perform an update to a mounted component. The componentWillReceiveProps and
   * shouldComponentUpdate methods are called, then (assuming the update isn't
   * skipped) the remaining update lifecycle methods are called and the DOM
   * representation is updated.
   *
   * By default, this implements React's rendering and reconciliation algorithm.
   * Sophisticated clients may wish to override this.
   *
   * @param {ReactReconcileTransaction} transaction
   * @param {ReactElement} prevParentElement
   * @param {ReactElement} nextParentElement
   * @internal
   * @overridable
   */
  updateComponent: function(
    transaction,
    prevParentElement,
    nextParentElement,
    prevUnmaskedContext,
    nextUnmaskedContext
  ) {
    var inst = this._instance;
    invariant(
      inst != null,
      'Attempted to update component `%s` that has already been unmounted ' +
      '(or failed to mount).',
      this.getName() || 'ReactCompositeComponent'
    );