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.
while (nextUnitOfWork !== null) {
          nextUnitOfWork = performUnitOfWork(nextUnitOfWork);
          if (nextUnitOfWork === null) {
            invariant(
              pendingCommit !== null,
              'Should have a pending commit. This error is likely caused by ' +
                'a bug in React. Please file an issue.',
            );
            
            priorityContext = TaskPriority;
            commitAllWork(pendingCommit);
            priorityContext = nextPriorityLevel;
            
            handleCommitPhaseErrors();
            
            if (
              nextPriorityLevel === NoWork ||
              nextPriorityLevel > minPriorityLevel ||
              nextPriorityLevel > TaskPriority
            ) {
              
              break;
            }
          }
        }
      } else if (deadline !== null) {
        
        while (nextUnitOfWork !== null && !deadlineHasExpired) {
          if (deadline.timeRemaining() > timeHeuristicForUnitOfWork) {