Prevent swipe to go back on first page in flutter

I have an issue that even when I'm on the main page, the user can still swipe back (from the edge) and hence end up on a black page, how do I prevent this?

Best regards

There's some more info here: https://api.flutter.dev/flutter/widgets/ModalRoute/addScopedWillPopCallback.html

    @override
    Widget build(BuildContext context) {
        return WillPopScope(//forbidden swipe in iOS(my ThemeData(platform: TargetPlatform.iOS,)
        onWillPop: ()async {
            return !(Navigator.of(context).userGestureInProgress);
        },
        child: <your child>,
        );
    }