Bug report

A static class property, after having been initialized as an empty array, is modified, e.g. by method calls of the same class or PHPUnit mock object callbacks in the same class. Yet PHPStan still believes the array is empty. Example output:
Offset (int|string) does not exist on array().

Code snippet that reproduces the problem

https://phpstan.org/r/0d08bf7b-5819-412f-a890-1b9a3caf9abd

Expected output

None

Coming from #1940.