fix: prevent crash when KeyboardChatScrollView unmounted

[kirillzyusko]

📜 Description

Fixed a crash on Android when using KeyboardChatScrollView.

💡 Motivation and Context

We may schedule a call to perform scrollTo later. But if the component is unmounted, then we will get a crash.

In this PR I'm adding a check to skip scrollTo operation if view was unmounted.

Based on bluesky-social/social-app#10673

📢 Changelog

JS

• skip scrollTo if ref is null;

🤔 How Has This Been Tested?

There is no way to test it at the moment, but CI is green 🟢

📸 Screenshots (if appropriate):

📝 Checklist

• CI successfully passed
• I added new mocks and corresponding unit-tests if library API was changed

[github-actions]

📊 Package size report

Current size	Target Size	Difference
318237 bytes	317920 bytes	317 bytes 📈

[github-actions]

• ** scrollViewRef check prevents potential crashes when ref is invalid or unmounted**
  Why: Without the check, calling scrollTo on an invalid ref could cause runtime errors, especially if the component has been unmounted.
  Fix: The added guard clause correctly prevents this scenario.

LGTM