fix(cloud_firestore): conditionally pass options to docChanges

[Ehesp]

Description

Since version 8.0.2 of the Firestore web sdk, it seems passing null to docChanges causes the underlying SDK to assume the user passed options, which causes a "null pointer exception".

This change wraps the options check, and doesn't pass arguments (undefined) instead.

Line of code: https://github.com/firebase/firebase-js-sdk/blob/626c05b36cfe7f91ac9b6aad730c0f04d6bb8c01/packages/firestore/src/exp/snapshot.ts#L445

Related Issues

Fixes #4127

Unblocks #5170

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Breaking Change

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[russellwheatley]

LGTM

[mikehardy]

Yes! This un blocks current js sdks and makes using all of the Auth emulator stuff official. Exciting!