We used to throw if event listener is not a function in Stack:

```js
ReactDOM.render(
  <h1 onClick={{}}>Hello World!</h1>,
  document.getElementById('container')
);
```

<img width="565" alt="screen shot 2017-08-08 at 3 41 08 pm" src="https://user-images.githubusercontent.com/810438/29077502-2646412e-7c50-11e7-8c99-3b7f6c0a2589.png">

Fiber silently ignores this.

I think we should throw. This would let us add support for objects (e.g. for passive listener configuration) if we want to in a minor rather than a major.
expect(container.firstChild.hasAttribute('dangerouslySetInnerHTML')).toBe(
        false,
      );
      ReactDOM.render(
        <my-component dangerouslySetInnerHTML={{__html: 'bye'}} />,
        container,
      );
      expect(container.firstChild.hasAttribute('dangerouslySetInnerHTML')).toBe(
        false,
      );
    });
    it('should render null and undefined as empty but print other falsy values', () => {
      var container = document.createElement('div');
      ReactDOM.render(
        <div dangerouslySetInnerHTML={{__html: 'textContent'}} />,
        container,
      );
      expect(container.textContent).toEqual('textContent');
      ReactDOM.render(<div dangerouslySetInnerHTML={{__html: 0}} />, container);
      expect(container.textContent).toEqual('0');
      ReactDOM.render(
        <div dangerouslySetInnerHTML={{__html: false}} />,
        container,
      );
      expect(container.textContent).toEqual('false');
      ReactDOM.render(
        <div dangerouslySetInnerHTML={{__html: ''}} />,
        container,
      );
      expect(container.textContent).toEqual('');