Property lookup from JavaScript in extended types doesn't always work

The attached test-case is a patch to the auto-tests to reproduce the issue. I'll also elaborate here what's going on:

QtObject {
id: root
property MyExtendedObject a;
a: MyExtendedObject

{ id: obj extendedProperty: 42; }

function getValue()

{ return obj.extendedProperty; }

}

Calling getValue() will fail and not return the expected value of 42.