Yes, this is either a bug in 7.2.0 or they really changed the way it works with null. Don't worry about it.
As I don't know yet what would be the best way to fix it (because, if it gets "fixed" in PHP 7.2.1 or so, then nothing should be fixed in Osclass part). If they make this behavior permanent in PHP, then it will be easy to deal with it, but it is best to wait for now.
Regards