QQuickStateGroup taking null pointers leads to crash

Since Qt 6.5.3, QQuickStateGroup no longer ignores appending null pointers to its states property. However, QQuickStateGroup::componentComplete() performs actions on the states objects without null checks. It doesn't even use asserts. This causes crashes which are really hard do analyze.

This issue appeared after switching to Qt 6.5.3 due to a QML binding with a type mismatch.

The following is the minimum scenario to reproduce the issue:

Item{
    states: ["test"]
} 

In Qt 6.5.2 this has been simply ignored. There wasn't even a warning.