To repro:
- Start the app with
npm start - Click anywhere outside the modal to try to close it
- You'll see an error
The problem is that renderSubtreeIntoContainer is returning null
instance of an instance. And this only happens on the first render, I
think, so we only hit this problem if we conditionally render the
Modal like this.state.open && <Modal> instead of <Modal open={this.state.open} />.