Propagating onEvent errors of EventListener not handled

In the Step - ["**Display data from Firestore**"](https://firebase.google.com/codelabs/firestore-android?index=..%2F..index#6), the provided code does not handle the case of propagating the **Listen errors** to the protected method `onError()` of `FirestoreAdapter`. If propagated, then only the user will be able to see a **Snackbar** in case of any **Listen errors** occurring due to improper **Query**, in the `onEvent()` callback of `EventListener`. This `onError()` method is overidden by subclasses of `FirestoreAdapter` to provide their own implementation for handling the `FirebaseFirestoreException` error passed to it.