StackView issue when "StackView.Immediate" is used.

[pra7]

I am getting following error "ReferenceError: stack is not defined" when i clicked on back to 1 button and not getting any error when i clicked on back to 2 button .

I will not get any error if i removed "StackView.Immediate", Below is the code:

import QtQuick 2.6
import QtQuick.Window 2.2
import QtQuick.Controls 2.2


Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("Stack view")

    MainForm {

        property alias stack:stack
        StackView
        {
            id: stack
            width: 360
            height: 360
            initialItem: comp1
        }

        Component
        {
            id:comp1
            Rectangle
            {
                id: page1
                color: "lightgreen"
                Button {
                    id: buttonPage1
                    text: "back to 2"
                    anchors.centerIn: parent
                    onClicked: {
                       stack.pop(StackView.Immediate)
                        stack.push(comp2, StackView.Immediate)

                    }
                }
                TextEdit {
                    id: te1
                    width: 105
                    height: 40
                    text: "enter"
                }
            }
        }
        Component
        {
            id:comp2
            Rectangle
            {
                id: page2

                color: "lightblue"
                Button {
                    id: buttonPage2
                    text: "back to 1"
                    anchors.centerIn: parent
                    onClicked: {
                        stack.pop(StackView.Immediate)
                        stack.push(comp1,StackView.Immediate)

                    }
                }
                TextEdit {
                    id: te2
                    width: 109
                    height: 29
                    text: "enter"
                }
            }
        }
    }
}