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.
isCommitting = true;
    if (__DEV__) {
      startCommitTimer();
    }
    pendingCommit = null;
    const root: FiberRoot = (finishedWork.stateNode: any);
    invariant(
      root.current !== finishedWork,
      'Cannot commit the same tree as before. This is probably a bug ' +
        'related to the return field. This error is likely caused by a bug ' +
        'in React. Please file an issue.',
    );
    if (
      nextPriorityLevel === SynchronousPriority ||
      nextPriorityLevel === TaskPriority
    ) {
      
      
      nestedUpdateCount++;
    }
     Reset this to null before calling lifecycles
    ReactCurrentOwner.current = null;
    let firstEffect;
    if (finishedWork.effectTag > PerformedWork) {