[Bug]- Exceptions occur when a user tries to logout

[Jaideep-C]

Issue Description:

There are two exceptions in the app which are occurring when a user tries to logout.

1. PersistentTabController was used after being disposed

   ════════ Exception caught by widgets library ═══════════════════════════════════
   The following assertion was thrown while finalizing the widget tree:
   A PersistentTabController was used after being disposed.
   Once you have called dispose() on a PersistentTabController, it can no longer be used.
   When the exception was thrown, this was the stack
   #0      ChangeNotifier._debugAssertNotDisposed.<anonymous closure>
   package:flutter/…/foundation/change_notifier.dart:117
   #1      ChangeNotifier._debugAssertNotDisposed
   package:flutter/…/foundation/change_notifier.dart:123
   #2      ChangeNotifier.dispose
   package:flutter/…/foundation/change_notifier.dart:212
   #3      PersistentTabController.dispose
   package:persistent_bottom_nav_bar/models/persistent-nav-bar-scaffold.widget.dart:37
   #4      _HomePageState.dispose
   package:talawa/…/pages/home_page.dart:50
   ...
   ════════════════════════════════════════════════════════════════════════════════

2. Tickers used by AnimationControllers are not disposed

   ════════ Exception caught by widgets library ═══════════════════════════════════
   The following assertion was thrown while finalizing the widget tree:
   _UrlPageState#45fca(tickers: tracking 21 tickers) was disposed with an active Ticker.
   _UrlPageState created a Ticker via its TickerProviderStateMixin, but at the time dispose() was called on the mixin, that Ticker was still active. All Tickers must be disposed before calling super.dispose().
   Tickers used by AnimationControllers should be disposed by calling dispose() on the AnimationController itself. Otherwise, the ticker will leak.

Issue Severity:

High, as these exceptions cause memory leaks.

Environment Details:

Mobile Device(Android-arm64)

$ flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, 2.0.3, on Microsoft Windows [Version 10.0.19042.870], locale en-IN)
[√] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
[√] Chrome - develop for the web  
[√] Android Studio (version 4.1.0)
[√] Connected device (3 available)

• No issues found!

Steps to reproduce issue:

To reproduce the issue follow these

1. log in to the App
2. navigate to the profilePage
3. click on Logout btn, then yes.

Snapshots/Videos:

Persistenttabcontroller-1.mp4

Tickerexception-1.mp4

Does this issue need immediate attention?

Yes!

Are you willing to work on this issue:

I am happy to fix the issue😊

[Jaideep-C]

The first exception of the issue is solved at #523 and the second part is solved at #521.
Thanks, @utkarshshendge for helping out 😊