Property of type extended with qmlRegisterExtendedType is ignored if an item of the to-be-extended type is created first

When running the attached example (having compiled the plugin first) with
qmlscene -I . main.qml
We get
file:///home/tsdgeos_work/extendedTypeBug/main.qml:6:5: QML Image: Cannot open: file:///home/tsdgeos_work/extendedTypeBug/thisShouldBeIgnoredByImport
qml: file:///home/tsdgeos_work/extendedTypeBug/thisShouldBeIgnoredByImport

This means that the Image {} in MyItem.qml is not getting the "source" property overridden by the "import ManglingImport 1.0" as it should.

If you uncomment the Image {} in MySingleton/MySingleton.qml it will work fine and we get
Ignoring the url you set to QUrl( "file:///home/tsdgeos_work/extendedTypeBug/thisShouldBeIgnoredByImport" )
qml: MoMoMoMo

I've traced this a bit and it seems to me that qmlRegisterExtendedType should make sure the object creator takes the new metaobject/propertycache into account even if it has already created an item for that type.