fix: fix js bottom tabs crashing on contacts in example

[chitrakshtarun]

PR Description

Bug fix.

Fixes the runtime crash in the JS Bottom Tabs example when switching to the Contacts tab:

Couldn't find the bottom tab bar height. Are you inside a screen in Native Bottom Tab Navigator?

Root cause: The Contacts.tsx screen is shared by all example navigators, and was using the useBottomTabBarHeight import. This threw because of a missing context in the JS implementation, as it used the JS implementation instead of the Native Implementation.

This fix should read from the context safely, and fallback to a nullish coalescence value to prevent any errors.

How to test?

• Run the example app.
• Scroll down to the JS Tabs examples.
• Navigate to the Contacts tabs.
• Contacts tabs should now render as intended and not throw an error.

Screenshots

js-bottom-tabs-repro.mov

Closes #533

[chitrakshtarun]

Hi @thiagobrez, hope pinging for this is fine!

This is my first PR in the repo, have made my best attempts to ensure the CONTRIBUTING.md guidelines are met. yarn typecheck and yarn lint return no errors.

Please let me know if the same looks fine, or if I should do any further changes before the PR is merged.