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.
effectfulFiber = effectfulFiber.alternate;
          capturedError = capturedErrors.get(effectfulFiber);
          capturedErrors.delete(effectfulFiber);
        }
      }
    }
    invariant(
      capturedError != null,
      'No error for given unit of work. This error is likely caused by a ' +
        'bug in React. Please file an issue.',
    );
    const error = capturedError.error;
    try {
      logCapturedError(capturedError);
    } catch (e) {
       
       
      console.error(e);
    }