This fixes a bug where games like "Don't Starve Together" wouldn't
capture because their actual render window is a completely different
window than their actual window on the screen.
So, because we already have the hook info by this point with the last
known window handle available, instead of using 0 here, we can just use
the window handle provided by the shared memory. And we didn't even
have to change the hook! That's nice.
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