Bug report

Hello,
I've ran into an issue in some legacy project after upgrading to version 2.1.25.
Basically there are two maps and one of them is used dynamically. PHPStan seems to make a union type out of it in the background (judging by the error message).

Although array_key_exists returns true, it still reports an error, that the key might not exist in one of the two maps.

Code snippet that reproduces the problem

https://phpstan.org/r/4c05958a-eefb-4335-b210-8680b9edfae1

Expected output

As it is a false positive, no error should be reported.

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