Given the following test case

``` jsx
function TestCmp() {
  return <span>{NaN}</span>;
}

ReactDOM.render(<TestCmp />, document.getElementById('app'));
```

Produces the following warning:

```
Warning: Component's children should not be mutated.
    in span (created by TestCmp)
    in TestCmp (created by Unknown)
```

This is probably caused by [this mutation check](https://github.com/facebook/react/blob/328fc75bc910032ff37dc9d93429fb14b476bd0d/src/renderers/shared/hooks/ReactChildrenMutationWarningHook.js#L34), which was introduced in 15.3.0, but it doesn't work for NaN, because NaN != NaN

try {
    fn.call(context, arg1, arg2, arg3, arg4, arg5);
  } catch (e) {
    warning(
      didHookThrowForEvent[event],
      'Exception thrown by hook while handling %s: %s',
      event,
      e + '\n' + e.stack
    );
    didHookThrowForEvent[event] = true;
  }
}
function emitEvent(event, arg1, arg2, arg3, arg4, arg5) {