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

var lifecycle = [];
        var TestComponent = React.createClass({
          componentWillMount: function() {
            lifecycle.push('componentWillMount');
          },
          componentDidMount: function() {
            lifecycle.push('componentDidMount');
          },
          getInitialState: function() {
            lifecycle.push('getInitialState');
            return {name: 'TestComponent'};
          },
          render: function() {
            lifecycle.push('render');
            return <span>Component name: {this.state.name}</span>;
          },