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.
ops.push('BrokenRender');
      throw new Error('Hello');
    }
    expect(() => {
      ReactNoop.flushSync(() => {
        ReactNoop.render(
          <RethrowErrorBoundary>
            Before the storm.
          </RethrowErrorBoundary>,
        );
        ReactNoop.render(
          <RethrowErrorBoundary>
            <BrokenRender />
          </RethrowErrorBoundary>,
        );
      });
    }).toThrow('Hello');
    expect(ops).toEqual([
      'RethrowErrorBoundary render',
      'BrokenRender',
      'RethrowErrorBoundary componentDidCatch',
    ]);
    expect(ReactNoop.getChildren()).toEqual([]);
  });
  it('applies batched updates regardless despite errors in scheduling', () => {
    ReactNoop.render(<span prop="a:1" />);
    expect(() => {
      ReactNoop.batchedUpdates(() => {