Bug report

Checking if an array key exist, and then throwing an exception/ returning when it does not makes it so the array can not be empty, even when it is unset

Code snippet that reproduces the problem

https://phpstan.org/r/74c5fd68-3156-4618-9b1e-a7db1cf3f0f6

Expected output

I'd expect no errors here, as the array can be empty