[Bug] [iOS] StateLayout error when enter and leave a page quickly

[taenito]

Description

I get this error when I enter and leave a page quickly with StateLayout

I call a API during OnAppearing and wait the reponse to change my State to None.
Loading (API call) -> None

SIGABRT: Object reference not set to an instance of an object

Stack traces from AppCenter :

VisualElementPackager.OnChildAdded (Xamarin.Forms.VisualElement view) D:\...\Xamarin.Forms.Platform.iOS\VisualElementPackager.cs:118
VisualElementPackager.OnChildAdded (System.Object sender, Xamarin.Forms.ElementEventArgs e) D:\...\Xamarin.Forms.Platform.iOS\VisualElementPackager.cs:171
Element.OnChildAdded (Xamarin.Forms.Element child) D:\...\Xamarin.Forms.Core\Element.cs:328
VisualElement.OnChildAdded (Xamarin.Forms.Element child) D:\...\Xamarin.Forms.Core\VisualElement.cs:832
Layout`1[T].OnChildAdded (Xamarin.Forms.Element child)
Layout.OnInternalAdded (Xamarin.Forms.View view) D:\...\Xamarin.Forms.Core\Layout.cs:444
Layout.InternalChildrenOnCollectionChanged (System.Object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) D:\...\Xamarin.Forms.Core\Layout.cs:434
(wrapper delegate-invoke) <Module>.invoke_void_object_NotifyCollectionChangedEventArgs(object,System.Collections.Specialized.NotifyCollectionChangedEventArgs)
ObservableCollection`1[T].OnCollectionChanged (System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
ObservableCollection`1[T].OnCollectionChanged (System.Collections.Specialized.NotifyCollectionChangedAction action, System.Object item, System.Int32 index)
ObservableCollection`1[T].InsertItem (System.Int32 index, T item)
Collection`1[T].Add (T item)
ObservableWrapper`2[TTrack,TRestrict].Add (TRestrict item)
StateLayoutController.SwitchToContent (System.Boolean animate)
AsyncMethodBuilderCore+<>c.<ThrowAsync>b__7_0 (System.Object state) /Library/Frameworks/Xamarin.iOS.framework/Versions/Current/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1021
NSAsyncSynchronizationContextDispatcher.Apply () /Users/.../_work/1/s/xamarin-macios/src/Foundation/NSAction.cs:178
(wrapper managed-to-native) UIKit.UIApplication.UIApplicationMain(int,string[],intptr,intptr)
UIApplication.Main (System.String[] args, System.IntPtr principal, System.IntPtr delegate) /Users/.../_work/1/s/xamarin-macios/src/UIKit/UIApplication.cs:86
UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) /Users/.../_work/1/s/xamarin-macios/src/UIKit/UIApplication.cs:65
Application.Main (System.String[] args) C:\...\Main.cs:12

Steps to Reproduce

Expected Behavior

Actual Behavior

Basic Information

• Version with issue: Nightly build - Tuesday, July 20, 2021 (7/20/2021)
• Last known good version:
• IDE:
• Platform Target Frameworks:
  • iOS: 11
  • Android:
  • UWP:
• Android Support Library Version:
• Nuget Packages: Nightly build - Tuesday, July 20, 2021 (7/20/2021)
• Affected Devices:

Workaround

Reproduction imagery

Reproduction Link