[CI] Fixed PHPStan issues

[barw4]

🎫 Issue	IBX-XXXXX

Description:

Aside from $container being nullable I don't think we can do much for the following:

        $location = new Location();
        $value = isset($location->notDefined);
        self::assertFalse($value);

        $value = isset($location->id);
        self::assertTrue($value);

which results in:

Property Ibexa\Contracts\Core\Repository\Values\Content\Location::$id (int) in isset() is not nullable.  
         🪪  isset.property

therefore I added these cases to baseline.

For QA:

Documentation:

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud