validateDOMNesting generates warnings for components that return null inside tbody

[gotbadger]

According to the doc on Render its ok for components to return null if nothing needs to be
rendered but this causes a warning from validateDOMNesting if used inside a tbody

var Component = React.createClass({
    render: function() {
      return null
    }
});
var Table = React.createClass({
    render: function() {
        return <table><tbody><Component /></tbody></table>;
    }
});

ReactDOM.render(
    <Table />,
    document.getElementById('container')
);

gives us the following warning:

Warning: validateDOMNesting(...): <noscript> cannot appear as a child of <tbody>. See Table > tbody > noscript.

[nabilfreeman]

well spotted 👍

[zpao]

It looks like we're going to make null actually render to comment nodes in #5451 so this should become a non-issue in the future.