`strlen`  wrongly narrows down string type

https://psalm.dev/r/f5d6d67011

It seems like Psalm think $lastLabel is a falsy-string (`$lastLabel: ''|'0'`) for some reason when I use a check like:
```php
if (strlen($lastLabel) === 2) {
        return $lastLabel;
    }
```

Not sure is it related to `strlen` other another part of this code