[Bug] ArgumentNullException when navigating before to a page with CameraView before another page is disposed

[thomasgalliker]

Description

Steps to Reproduce

1. Navigate to a page containing CameraView.
2. Go back.
3. Navigate very quickly back to the previously opened page which contains an instance of CameraView.

Expected Behavior

• Wait until everything is disposed and re-initialize CameraView again.

Actual Behavior

• App crashes.

Basic Information

• Version with issue: 1.4.25-pre
• Last known good version: N/A

Screenshots, Attachments, Links

System.ArgumentNullException: Value cannot be null. (Parameter 'source')
   at System.Linq.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument)
   at System.Linq.Enumerable.Select[NSNumber,Single](IEnumerable`1 source, Func`2 selector)
   at CameraScanner.Maui.CameraManager.UpdateDeviceSwitchZoomFactors()
   at CameraScanner.Maui.CameraManager.StartAsync()
   at CameraScanner.Maui.CameraManager.UpdateCameraEnabled()
   at System.Threading.Tasks.Task.<>c.<ThrowAsync>b__128_0(Object state)
   at Foundation.NSAsyncSynchronizationContextDispatcher.Apply() in /Users/builder/azdo/_work/1/s/xamarin-macios/src/Foundation/NSAction.cs:line 179
   at UIKit.UIApplication.UIApplicationMain(Int32 argc, String[] argv, IntPtr principalClassName, IntPtr delegateClassName) in /Users/builder/azdo/_work/1/s/xamarin-macios/src/UIKit/UIApplication.cs:line 61
   at UIKit.UIApplication.Main(String[] args, Type principalClass, Type delegateClass) in /Users/builder/azdo/_work/1/s/xamarin-macios/src/UIKit/UIApplication.cs:line 96
   at PatientApp.Program.Main(String[] args) in /Users/thomasgalliker/src/gitlab/benecura-ng-2/PatientApp/Platforms/iOS/Program.cs:line 13