The argument type 'int?' can't be assigned to the parameter type 'int'

this is RadioModel.dart I am a beginner in flutter and I want to display my JSON file data on vx swipper.builder but i don't know whats going on here when i pass item count i face this error i know i am doing something wrong and i can't fix this I am a beginner in flutter and I want to display my JSON file data on vx swipper.builder but i don't know whats going on here when i pass item count i face this error i know i am doing something wrong and i can't fix this I am a beginner in flutter and I want to display my JSON file data on vx swipper.builder but i don't know whats going on here when i pass item count i face this error i know i am doing something wrong and i can't fix this

import 'dart:convert';

class MyRadioList {
  static List<MyRadio>? radios;

  // Get Item by ID
  MyRadio getById(int id) =>
      radios!.firstWhere((element) => element.id == id, orElse: null);

  // Get Item by position
  MyRadio getByPosition(int pos) => radios![pos];
}

class MyRadio {
  final int id;
  final int order;
  final String name;
  final String tagline;
  final String color;
  final String desc;
  final String url;
  final String category;
  final String icon;
  final String image;
  final String lang;
  MyRadio({
    required this.id,
    required this.order,
    required this.name,
    required this.tagline,
    required this.color,
    required this.desc,
    required this.url,
    required this.category,
    required this.icon,
    required this.image,
    required this.lang,
  });

  factory MyRadio.fromMap(Map<String, dynamic> map) {
    return MyRadio(
      id: map['id'],
      order: map['order'],
      name: map['name'],
      tagline: map['tagline'],
      color: map['color'],
      desc: map['desc'],
      url: map['url'],
      category: map['category'],
      icon: map['icon'],
      image: map['image'],
      lang: map['lang'],
    );
  }

  toMap() => {
        "id": id,
        "order": order,
        "name": name,
        "tagline": tagline,
        "color": color,
        "desc": desc,
        "url": url,
        "category": category,
        "icon": icon,
        "image": image,
        "lang": lang,
      };
}

// this is HomePage.dart

import 'dart:convert';
import 'dart:ffi';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_application_1/models/RadioModel.dart';
import 'package:flutter_application_1/utils/Ai_Utils.dart';
import 'package:velocity_x/velocity_x.dart';

class HomePage extends StatefulWidget {
  const HomePage({Key? key}) : super(key: key);

  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  //get daata from radio model
  @override
  void initstate() {
    super.initState();
    fetchradios();
  }

  fetchradios() async {
    final radioJson = await rootBundle.loadString("assets/radio.json");
    final decodedData = jsonDecode(radioJson);
    MyRadioList.radios = List.from(decodedData)
        .map<MyRadio>(((radio) => MyRadio.fromMap(radio)))
        .toList();
    setState(() {});
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      drawer: Drawer(),
      body: Stack(children: [
        VxAnimatedBox()
            .withGradient(LinearGradient(
              colors: [AiColors.primaryColor1, AiColors.primaryColor2],
              begin: Alignment.topLeft,
              end: Alignment.bottomRight,
            ))
            .size(context.screenWidth, context.screenHeight)
            .make(),
        AppBar(
          title: "AI Radio".text.xl4.bold.white.make().shimmer(
              primaryColor: Vx.purple300, secondaryColor: Colors.white),
          elevation: 0.0,
          backgroundColor: Colors.transparent,
          centerTitle: true,
        ).h(100.0).p16(),
        VxSwiper.builder(
            itemCount: MyRadioList.radios?.length,      // error line
            itemBuilder: (context, index) {
              final rad = MyRadioList.radios![index];
              return VxBox(child: ZStack([]))
                  .bgImage(DecorationImage(image: NetworkImage(rad.image)))
                  .make();
            })
      ]),
    );
  }
}