Bug report

If I'm adding some key to array in foreach (modifying by reference), after this foreach PHPStan doesn't know this new key.

Code snippet that reproduces the problem

https://phpstan.org/r/50a73119-7090-4209-9fd7-4cef743b7760
https://3v4l.org/vDNLo

Expected output

No errors

I tried to initialize that new key in original array with null:
https://phpstan.org/r/d0762209-6772-4a55-9299-e3612f505b28

but error just change to comparing null with null which is not true for first n - 1 elements