FormSpy errors are different during every render, even if nothing changes

Take this example: https://codesandbox.io/s/react-final-form-field-arrays-p7ntw?file=/index.js

- Add a row and leave it empty (to have failing validation in the array element).
- Type something in the company field outside the array
- `onChange` of the FormSpy that is only subscribed to `errors` fires on every keypress in that field as long as the array contains any errors

Combined with a setState in the onChange callback this can easily result in a react update loop freezing the app.

Expected behavior: onChange only triggering when there's an actual change.