fix: race condition between keyboardWillHide and KVO

📜 Description

Fixed race condition between keyboardWillHide and KVO.

💡 Motivation and Context

The problem is that we dispatch syncUpLayout asynchronously: https://github.com/kirillzyusko/react-native-keyboard-controller/blob/091af29004ff756614cd240e488754a3fe477569/ios/observers/FocusedInputObserver.swift#L172-L174

And here we may have a race condition: KVO can dispatch an even, after that keyboardWillHide can be triggered, and finally we dispatch syncUpLayout (but the problem is that by this time currentInput will be already nil and we've already dispatched an event noFocusedInput -> eventually we'll get a crash when we'll try to read absoluteY from layout property).

To fix this problem we had two ways:

dispatch syncUpLayout synchronously - for that we had to change quite a lot of code (and I initially decided that it will take more code without significant advantages, thats why I dispatch currently asynchronously it)
check that currentInput is present <- that's what I do in this PR.

📢 Changelog

iOS

check that currentInput is actually present before sending an event;

🤔 How Has This Been Tested?

Tested manually on iPhone 15 Pro.

📸 Screenshots (if appropriate):

No sense to attach a video, because it's very hard to reproduce the problem (I could reproduce it by swipe a screen back and forth and after ~30 seconds I was getting a crash).

📝 Checklist

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

kirillzyusko / react-native-keyboard-controller