Fix warning after static analyzes

example/lib/main.dart

@@ -46,10 +46,10 @@ class MyApp extends StatelessWidget {
 }
 }
 
 
 class PermissionWidget extends StatefulWidget {
 class PermissionWidget extends StatefulWidget {
-  final PermissionGroup _permissionGroup;
-
   const PermissionWidget(this._permissionGroup);
   const PermissionWidget(this._permissionGroup);
 
 
+  final PermissionGroup _permissionGroup;
+
   @override
   @override
   _PermissionState createState() => _PermissionState(_permissionGroup);
   _PermissionState createState() => _PermissionState(_permissionGroup);
 }
 }