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.
resetContextStack();
      nextUnitOfWork = createWorkInProgress(
        highestPriorityRoot.current,
        highestPriorityLevel,
      );
      return;
    }
    nextPriorityLevel = NoWork;
    nextUnitOfWork = null;
    return;
  }
  function commitAllHostEffects() {
    while (nextEffect !== null) {
      if (__DEV__) {
        ReactDebugCurrentFiber.setCurrentFiber(nextEffect, null);
        recordEffect();
      }
      const effectTag = nextEffect.effectTag;
      if (effectTag & ContentReset) {
        config.resetTextContent(nextEffect.stateNode);
      }
      if (effectTag & Ref) {
        const current = nextEffect.alternate;
        if (current !== null) {
          commitDetachRef(current);
        }