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.
}
            }
          } else {
            deadlineHasExpired = true;
          }
        }
      }
      
      
      switch (nextPriorityLevel) {
        case SynchronousPriority:
        case TaskPriority:
          
          
          if (nextPriorityLevel <= minPriorityLevel) {
            continue loop;
          }
          break loop;
        case HighPriority:
        case LowPriority:
        case OffscreenPriority:
          
          if (deadline === null) {
            
            
            break loop;
          }
          
          if (!deadlineHasExpired && nextPriorityLevel <= minPriorityLevel) {