Exception has occurred: CLR/System.NullReferenceException due to DashboardTabbedPageHandler

Question

My home page is a flyout page with a tabbed page as the detail and a menu pop up page as the flyout. My problem is I have a handler for tabbed page and while using it I am getting below exception:

Exception has occurred: CLR/System.NotImplementedException

•   An unhandled exception of type 'System.NotImplementedException' occurred in Microsoft.iOS.dll: 'The method or operation is not implemented.'    at UIKit.UIApplication.xamarin_UIApplicationMain(Int32 argc, IntPtr argv, IntPtr principalClassName, IntPtr delegateClassName, IntPtr* gchandle)   at UIKit.UIApplication.UIApplicationMain(Int32 argc, String[] argv, IntPtr principalClassName, IntPtr delegateClassName)   at UIKit.UIApplication.Main(String[] args, Type principalClass, Type delegateClass)   at Inventiva.Program.Main(String[] args) in /Users/sreejith.sreenivasan/Downloads/inv-hnas337-mobile-patient/Inventiva/Platforms/iOS/Program.cs:line 13

Below is my DashboardTabbedPageHandler.cs:

using System;
using UIKit;
using Microsoft.Maui.Handlers;
using Microsoft.Maui.Controls;
using Xamarin.Forms.Clinical6.Views;

namespace MAUI.Clinical6.Platforms.iOS.Controls
{
    public class DashboardTabbedPageHandler : TabbedViewHandler
    {
        protected override void ConnectHandler(UIView platformView)
        {
            base.ConnectHandler(platformView);

            if (VirtualView is DashboardTabPage dashboardTabPage)
            {
                dashboardTabPage.DashboardBadgeEvent += OnDashboardBadgeEvent;
            }
        }

        protected override void DisconnectHandler(UIView platformView)
        {
            if (VirtualView is DashboardTabPage dashboardTabPage)
            {
                dashboardTabPage.DashboardBadgeEvent -= OnDashboardBadgeEvent;
            }

            base.DisconnectHandler(platformView);
        }

        private void OnDashboardBadgeEvent(object sender, int count)
        {
            UpdateBadge(count);
        }

        private void UpdateBadge(int count)
        {
            try
            {
                // Get the UITabBarController from the root view hierarchy
                UITabBarController tabBarController = null;

                var window = UIApplication.SharedApplication.KeyWindow;
                var rootController = window.RootViewController;

                if (rootController is UITabBarController tbc)
                {
                    tabBarController = tbc;
                }
                else if (rootController is UINavigationController nav && nav.ViewControllers.Length > 0)
                {
                    tabBarController = nav.ViewControllers[0] as UITabBarController;
                }

                if (tabBarController?.TabBar?.Items == null || tabBarController.TabBar.Items.Length == 0)
                    return;

                var tabBarItem = tabBarController.TabBar.Items[0];

                if (count == 0)
                {
                    RemoveBadge(tabBarItem);
                    return;
                }

                tabBarItem.BadgeColor = UIColor.FromRGB(190, 23, 23); // #BE1717
                tabBarItem.BadgeValue = count.ToString();
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex);
            }
        }

        private void RemoveBadge(UITabBarItem tabBarItem)
        {
            if (tabBarItem == null)
                return;

            tabBarItem.BadgeColor = UIColor.Clear;
            tabBarItem.BadgeValue = string.Empty;
        }
    }
}

I tried to remove this handler by commenting its registration in MAUIProgram.cs, but still getting another exception.

//Commecnted below
handlers.AddHandler(typeof(DashboardTabPage), typeof(DashboardTabbedPageHandler)); 

Exception getting:

Exception has occurred: CLR/System.NullReferenceException

•   An unhandled exception of type 'System.NullReferenceException' occurred in Microsoft.iOS.dll: 'Object reference not set to an instance of an object.'    at UIKit.UIApplication.xamarin_UIApplicationMain(Int32 argc, IntPtr argv, IntPtr principalClassName, IntPtr delegateClassName, IntPtr* gchandle)   at UIKit.UIApplication.UIApplicationMain(Int32 argc, String[] argv, IntPtr principalClassName, IntPtr delegateClassName)   at UIKit.UIApplication.Main(String[] args, Type principalClass, Type delegateClass)   at Inventiva.Program.Main(String[] args) in /Users/sreejith.sreenivasan/Downloads/inv-hnas337-mobile-patient/Inventiva/Platforms/iOS/Program.cs:line 13

In tabs the firsttab is a list of alerts and I want to show the unread alert count on it as a badge and that logic is inside of this handler.