badeggg

Use `useIsFocused` may lead to app crash

12

### Current behavior Use `useIsFocused` may lead to app crash The causing code lines are https://github.com/react-navigation/react-navigation/blob/52a3234b7aaf4d4fcc9c0155f44f3ea2233f0f40/packages/core/src/useIsFocused.tsx#L16-L23 I must say that if we write code lines like: ```tsx const [foo, setFoo]...