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.
invariant(
            nextPriorityLevel === TaskPriority,
            'Commit phase errors should be scheduled to recover with task ' +
              'priority. This error is likely caused by a bug in React. ' +
              'Please file an issue.',
          );
        }
      }
    }
  }
  function workLoop(
    minPriorityLevel: PriorityLevel,
    deadline: Deadline | null,
  ) {
    if (pendingCommit !== null) {
      priorityContext = TaskPriority;
      commitAllWork(pendingCommit);
      handleCommitPhaseErrors();
    } else if (nextUnitOfWork === null) {
      resetNextUnitOfWork();
    }
    if (nextPriorityLevel === NoWork || nextPriorityLevel > minPriorityLevel) {
      return;
    }
    
    
    priorityContext = nextPriorityLevel;
    loop: do {
      if (nextPriorityLevel <= TaskPriority) {