Positions of elements in RowLayout are not recalculated after one of them was hidden

ApplicationWindow {
    id: appWin
    width: 640
    height: 480
    visible: true

    toolBar: ToolBar {
        id: tb
        style: ToolBarStyle {
            padding { left: 4; right: 4; top: 2; bottom: 1 }
        }
        Flickable {
            width: tbRow.width
            height: tbRow.height
            contentWidth: tbRow.implicitWidth
            contentHeight: tbRow.implicitHeight
            clip: true
            RowLayout {
                id: tbRow
                width: appWin.width-8
                spacing: 8
                ToolButton { width: 48; height: 48; text: "A"
                             onClicked: lastBtn.visible = !lastBtn.visible}
                ToolButton { width: 48; height: 48; text: "B" }
                ToolButton { width: 48; height: 48; text: "C" }
                ToolButton { width: 48; height: 48; text: "D" }
                ToolButton { width: 48; height: 48; text: "E" }
                ToolButton { width: 48; height: 48; text: "F" }
                ToolButton { width: 48; height: 48; text: "G" }
                Item { Layout.fillWidth: true}
                ToolButton { width: 48; height: 48; text: "Close"; id: lastBtn }
            }
        }
    }
}