WebAction cause "Invalid attached object assignment"

webberg

Hello,
I add WebEngineView in QML, and hope to disable right button menu. I find WebAction maybe disable it from assistant. So I write the following code:

WebEngineView {
            id: viewer
            objectName: "webViewer"
            focus: true
            anchors.fill: parent
            WebAction: Qt.NoWebAction
}

But when I run it, it tell me "qrc:/qml/WebView/WebView.qml:323:13: Invalid attached object assignment" in WebAction: Qt.NoWebAction line. So what happened?