Qt3D NodeInstantiator using Times the index out of range error record

Recently added to the batch used NodeInstantiator entity
beginning with the collapse of the program has been
an error code is as follows:

// main.qml
ApplicationWindow {
    ......
    Loader {
        id: root_loader
    }
    ......
    Connections {
        target: manage_system
        onSystemInited: root_loader.source = "MainWindow.qml"
    }
    ......
}

// MainWindow.qml
Rectangle {
    Scene3D {
        id: scene_3d
        aspect: ["logic", "input]
        entity: SceneEntity {
            ......
            NodeInstantiator {
                model: 2
                delegate: Entity {
                    ......
                }
            }
            ......
        }
    }
}

This code structure substantially similar to the above, for simplicity of the model can be written NodeInstantiator 2

manage_system is c ++ to write a QObject subclass, store some load incoming data

It emits a signal manage_system systemInited initialization is complete.

Loader is because with hope after manage_system complete initialization, go to load some controls (information depends on manage_system)

However, the collapse of the reasons for the program is to use the Loader, into the following structure like this

// MainWIndow.qml
Rectangle {
    Connections {
        target: root_loader
        onLoaded: instantiator.model = 2
    }
    Scene3D {
        id: scene_3d
        aspect: ["logic", "input]
        entity: SceneEntity {
            ......
            NodeInstantiator {
                id: instantiator
                // model: 2  /* 注意这里没有指定model，延时初始化model */
                delegate: Entity {
                    ......
                }
            }
            ......
        }
    }
}

I guess the problem is the first piece of code to initialize the timing instantiator premature (state parent is not yet Loader.Ready)
so specified in the model and then loaded root_loader