Invalid `property.unusedType` report for nullable WeakMap property (broken since 1.12.4)

### Bug report

See snippet, PHPStan shows 0 errors in `1.12.3`.

### Code snippet that reproduces the problem

https://phpstan.org/r/302a8b9a-5681-47cf-9c43-26db858b19a9

### Expected output

No errors.

### Did PHPStan help you today? Did it make you happy in any way?

_No response_