[Reg 6.2 -> 6.3] qmlcachegen failure suspecting for recognizing qml type

The attached example works on 6.2 but cannot get built on 6.3 with a hidden failure of qmlcachegen (it is not explicitly saying the failure is because of qmlcachegen in QtC, but if build in command line it will say qmlcachegen returned with an error code) .

If change line #4 in BadType.qml to be:

required property Item picker

the build will then pass