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.
} finally {
      isBatchingUpdates = previousIsBatchingUpdates;
       
       
      if (!isPerformingWork && !isBatchingUpdates) {
        performWork(TaskPriority, null);
      }
    }
  }
  function unbatchedUpdates<A>(fn: () => A): A {
    const previousIsUnbatchingUpdates = isUnbatchingUpdates;
    const previousIsBatchingUpdates = isBatchingUpdates;
     
    isUnbatchingUpdates = isBatchingUpdates;
    isBatchingUpdates = false;
    try {
      return fn();
    } finally {
      isBatchingUpdates = previousIsBatchingUpdates;
      isUnbatchingUpdates = previousIsUnbatchingUpdates;
    }
  }
  function flushSync<A>(batch: () => A): A {
    const previousIsBatchingUpdates = isBatchingUpdates;
    const previousPriorityContext = priorityContext;
    isBatchingUpdates = true;
    priorityContext = SynchronousPriority;
    try {
      return batch();
    } finally {