fix: cannot access 'unobserve' before initialization

[kik4]

Hello!
I got an error ReferenceError: cannot access 'unobserve' before initialization when IntersectionObserver is undefined, fallbackInView and triggerOnce of useInView is true.
When that condition is met, 'unobserve' is before initialization at line 73 in useInView.tsx.
So I added an initialization line and created this PR. Please check it.

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Name	Status	Preview	Updated
react-intersection-observer	✅ Ready (Inspect)	Visit Preview	Oct 23, 2022 at 8:12AM (UTC)

[codesandbox-ci]

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Sandbox	Source
useInView	Configuration
InView render props	Configuration
InView plain children	Configuration

[thebuilder]

Can you make sandbox that replicates it? I fail to see how this PR changes anything.
There is already an if to check unobserve exists before calling it.

[kik4]

Here it is.
These are set IntersectionObserver = undefined for fallback behavior and the options of useInView.
v9.4.0: https://codesandbox.io/s/useinview-forked-dt66bx (Doesn't work)
this PR: https://codesandbox.io/s/useinview-forked-pwr0hr

[thebuilder]

Ah - Okay, i see - Makes sense.

[thebuilder]

🎉 This PR is included in version 9.4.1 🎉

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