Demonstrates a possible regression in PyQt5.8 where calling QJSValue.toVariant() on a javascript object passed from QML which contains null as a value of one of its attributes, leads to this error: TypeError: unable to convert a C++ 'QVariantMap' instance to a Python object.

test.py

import sys
from PyQt5.QtCore import QObject, pyqtSlot
from PyQt5.QtCore import QVariant
from PyQt5.QtQml import QQmlApplicationEngine
from PyQt5.QtWidgets import QApplication


class Context(QObject):

    @pyqtSlot(QVariant)
    def test(self, data):
        print(data.toVariant())


application = QApplication(sys.argv)

context = Context()

engine = QQmlApplicationEngine()
engine.rootContext().setContextProperty('context', context)
engine.load('test.qml')

sys.exit(application.exec_())

test.qml

import QtQuick 2.0
import QtQuick.Window 2.0

Window {
    visible: true
    Component.onCompleted: context.test({'test': null})
}