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.
container,
      );
      
      
      expect(ops).toEqual(['B']);
      ops = [];
      
      click(node);
      expect(ops).toEqual(['A']);
    });
    it('should not crash encountering low-priority tree', () => {
      ReactDOM.render(
        <div hidden={true}>
          <div />
        </div>,
        container,
      );
    });
    it('should not warn when rendering into an empty container', () => {
      spyOn(console, 'error');
      ReactDOM.render(<div>foo</div>, container);
      expect(container.innerHTML).toBe('<div>foo</div>');
      ReactDOM.render(null, container);
      expect(container.innerHTML).toBe('');
      expectDev(console.error.calls.count()).toBe(0);
      ReactDOM.render(<div>bar</div>, container);
      expect(container.innerHTML).toBe('<div>bar</div>');
      expectDev(console.error.calls.count()).toBe(0);
    });
    it('should warn when replacing a container which was manually updated outside of React', () => {