check null safety

lib/domain/vo/privilege.dart

@@ -1,20 +1,24 @@
 import 'package:fcs/domain/constants.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter_icons/flutter_icons.dart';
+import 'package:flutter_icons_null_safety/flutter_icons_null_safety.dart';
 import 'package:font_awesome_flutter/font_awesome_flutter.dart';
 
 class Privilege {
   String id;
-  String name;
-  String desc;
-  bool sysAdminOnly = true;
-  bool isChecked = false;
+  String? name;
+  String? desc;
+  bool? sysAdminOnly = true;
+  bool? isChecked = false;
 
-  IconData iconData;
+  IconData? iconData;
 
   Privilege(
-      {this.id, this.name, this.desc, this.isChecked, this.sysAdminOnly}) {
+      {required this.id,
+      this.name,
+      this.desc,
+      this.isChecked,
+      this.sysAdminOnly}) {
     if (this.id == privilege_admin) {
       iconData = MaterialCommunityIcons.account_tie;
     } else if (this.id == privilege_support) {