Three points from discussion in https://github.com/reactjs/react-redux/issues/756:

* Due to https://bugs.chromium.org/p/chromium/issues/detail?id=701371, environments like CodeSandbox show `Error: null` in our “React caught an error” warning. Let’s consider skipping both as they’re not very useful and look like a bug. `Error: null` looks like a separate error and draws attention away from the real error just above.

* In any case we should probably not print `The error was thrown at:` if we don’t have a JS stack.

* There is a related issue. What do we pass to error boundary if we caught `null`? It seems that most error boundaries will intuitively do something like `if (this.state.error)` or read `error.message`, which `null` will break. There are other falsy values too like `''` and `undefined`. My proposal is we always wrap primitives into our own `Error` objects that we pass to the boundary.
return this.props.children;
      }
    }
    ReactNoop.render(
      <Parent>
        <Parent>
          <BrokenRenderAndUnmount />
        </Parent>
      </Parent>,
    );
    ReactNoop.flush();
    inst.setState({fail: true});
    expect(() => {
      ReactNoop.flush();
    }).toThrowError('Hello.');
    expect(ops).toEqual([
      
      
      'Parent componentWillUnmount [!]',
      'Parent componentWillUnmount [!]',
      'BrokenRenderAndUnmount componentWillUnmount',
    ]);
    expect(ReactNoop.getChildren()).toEqual([]);
  });
  it('does not interrupt unmounting if detaching a ref throws', () => {
    var ops = [];
    class Bar extends React.Component {