NullReferenceException when trying to remove selected item in NavigationView 2.1.0-preview6

[OleRoss]

Describe the bug
Following bug 572, when I try to clear the items, I get a NullReferenceException.

Unhandled exception. System.NullReferenceException: Object reference not set to an instance of an object.
   at FluentAvalonia.UI.Controls.NavigationView.RaiseItemInvoked(Object item, Boolean isSettings, NavigationViewItemBase container, NavigationRecommendedTransitionDirection recDir)
   at FluentAvalonia.UI.Controls.NavigationView.ChangeSelection(Object prevItem, Object nextItem)
   at FluentAvalonia.UI.Controls.NavigationView.OnSelectedItemPropertyChanged(Object oldItem, Object newItem)
   at FluentAvalonia.UI.Controls.NavigationView.OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
   at Avalonia.AvaloniaObject.OnPropertyChangedCore(AvaloniaPropertyChangedEventArgs change)
   at Avalonia.Animation.Animatable.OnPropertyChangedCore(AvaloniaPropertyChangedEventArgs change)
   at Avalonia.AvaloniaObject.RaisePropertyChanged[T](AvaloniaProperty`1 property, Optional`1 oldValue, BindingValue`1 newValue, BindingPriority priority, Boolean isEffectiveValue)
   at Avalonia.AvaloniaObject.SetAndRaise[T](DirectPropertyBase`1 property, T& field, T value)
   at FluentAvalonia.UI.Controls.NavigationView.set_SelectedItem(Object value)
   at FluentAvalonia.UI.Controls.NavigationView.SetSelectedItemAndExpectItemInvokeWhenSelectionChangedIfNotInvokedFromAPI(Object selItem)
   at FluentAvalonia.UI.Controls.NavigationView.OnSelectionModelSelectionChanged(Object sender, SelectionModelSelectionChangedEventArgs e)
   at FluentAvalonia.UI.Controls.SelectionModel.OnSelectionChanged()
   at FluentAvalonia.UI.Controls.SelectionModel.OnSelectionInvalidatedDueToCollectionChange()
   at FluentAvalonia.UI.Controls.SelectionNode.OnSourceListChanged(Object dataSource, NotifyCollectionChangedEventArgs args)
   at Avalonia.Controls.ItemsSourceView.Avalonia.Controls.Utils.ICollectionChangedListener.Changed(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
   at Avalonia.Controls.Utils.CollectionChangedEventManager.Entry.<Avalonia.Utilities.IWeakEventSubscriber<System.Collections.Specialized.NotifyCollectionChangedEventArgs>.OnEvent>g__Notify|6_0(INotifyCollectionChanged incc, NotifyCollectionChangedEventArgs args, WeakReference`1[] listeners)
   at Avalonia.Controls.Utils.CollectionChangedEventManager.Entry.Avalonia.Utilities.IWeakEventSubscriber<System.Collections.Specialized.NotifyCollectionChangedEventArgs>.OnEvent(Object notifyCollectionChanged, WeakEvent ev, NotifyCollectionChangedEventArgs e)
   at Avalonia.Utilities.WeakEvent`2.Subscription.OnEvent(Object sender, TEventArgs eventArgs)
   at Avalonia.Utilities.WeakEvents.<>c__DisplayClass5_0.<.cctor>b__5(Object _, NotifyCollectionChangedEventArgs e)
   at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
   at AvaloniaTests.ViewModels.MainWindowViewModel.Test() in C:\Users\OleRosskamp\RiderProjects\AvaloniaTests\AvaloniaTests\ViewModels\MainWindowViewModel.cs:line 16
   at System.Threading.Tasks.Task.<>c.<ThrowAsync>b__128_0(Object state)
   at Avalonia.Threading.SendOrPostCallbackDispatcherOperation.InvokeCore()
   at Avalonia.Threading.DispatcherOperation.Execute()
   at Avalonia.Threading.Dispatcher.ExecuteJob(DispatcherOperation job)
   at Avalonia.Threading.Dispatcher.ExecuteJobsCore(Boolean fromExplicitBackgroundProcessingCallback)
   at Avalonia.Threading.Dispatcher.Signaled()
   at Avalonia.Win32.Win32DispatcherImpl.DispatchWorkItem()
   at Avalonia.Win32.Win32Platform.WndProc(IntPtr hWnd, UInt32 msg, IntPtr wParam, IntPtr lParam)
   at Avalonia.Win32.Interop.UnmanagedMethods.DispatchMessage(MSG& lpmsg)
   at Avalonia.Win32.Win32DispatcherImpl.RunLoop(CancellationToken cancellationToken)
   at Avalonia.Threading.DispatcherFrame.Run(IControlledDispatcherImpl impl)
   at Avalonia.Threading.Dispatcher.PushFrame(DispatcherFrame frame)
   at Avalonia.Threading.Dispatcher.MainLoop(CancellationToken cancellationToken)
   at Avalonia.Controls.ApplicationLifetimes.ClassicDesktopStyleApplicationLifetime.Start(String[] args)
   at Avalonia.ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime(AppBuilder builder, String[] args, Action`1 lifetimeBuilder)
   at AvaloniaTests.Program.Main(String[] args) in C:\Users\OleRosskamp\RiderProjects\AvaloniaTests\AvaloniaTests\Program.cs:line 13

Screenshots
Minimal Repo: https://github.com/OleRoss/AvaloniaTests/tree/fe2bdf7f811452f934bf975e09f2cd06069a727a

The repo is the same as before, I just updated to preview6 and avalonia rc1.
Steps to reproduce:

• Select the first nav-view item (do not click on button)
• Click on button
  -> Exception

Desktop/Platform (please complete the following information):

• OS: Windows 11
• FluentAvalonia Version 2.1.0-preview6
• Avalonia Version 11.1.0-rc1