Set default keyboard state

[piaskowyk]

Summary

This PR addresses a requested issue that randomly occurs on some Android devices:

java.lang.NullPointerException: Attempt to invoke virtual method 'int com.swmansion.reanimated.keyboard.KeyboardState.asInt()' on a null object reference
        at com.swmansion.reanimated.keyboard.KeyboardAnimationManager.notifyAboutKeyboardChange(KeyboardAnimationManager.java:45)

This NullPointerException was likely caused by the lack of a default value for the mState field.