[Bug] Hard crash when using public key authentication with smartcards

[einalex]

Describe the bug
App crashes hard when using ssh public key authentication with smartcards

To Reproduce
Steps to reproduce the behavior:

1. add public key file to connection profile
2. click connect
3. See error

Expected behavior
Gracefully provide an error message.

Screenshots

Unhandled exception. Renci.SshNet.Common.SshException: Invalid private key file.
   at Renci.SshNet.PrivateKeyFile.Open(Stream privateKey, String passPhrase)
   at Renci.SshNet.PrivateKeyFile..ctor(Stream privateKey)
   at Slithin.Models.LoginInfo.GetKey() in /home/runner/work/Slithin/Slithin/Source/Slithin/Models/LoginInfo.cs:line 28
   at Slithin.ViewModels.ConnectionWindowViewModel.Connect(Object obj) in /home/runner/work/Slithin/Slithin/Source/Slithin/ViewModels/ConnectWindowViewModel.cs:line 148
   at Slithin.Core.MVVM.DelegateCommand.Execute(Object parameter) in /home/runner/work/Slithin/Slithin/Source/Libraries/Slithin.Core/MVVM/DelegateCommand.cs:line 32
   at Avalonia.Controls.Button.OnClick() in /_/src/Avalonia.Controls/Button.cs:line 323
   at Avalonia.Controls.Button.OnPointerReleased(PointerReleasedEventArgs e) in /_/src/Avalonia.Controls/Button.cs:line 364
   at Avalonia.Interactivity.RoutedEvent.<>c__DisplayClass23_0.<AddClassHandler>b__0(ValueTuple`2 args) in /_/src/Avalonia.Interactivity/RoutedEvent.cs:line 94
   at System.Reactive.AnonymousObserver`1.OnNextCore(T value) in /_/Rx.NET/Source/src/System.Reactive/AnonymousObserver.cs:line 67
   at System.Reactive.ObserverBase`1.OnNext(T value) in /_/Rx.NET/Source/src/System.Reactive/ObserverBase.cs:line 36
   at System.Reactive.Subjects.Subject`1.OnNext(T value) in /_/Rx.NET/Source/src/System.Reactive/Subjects/Subject.cs:line 145
   at Avalonia.Interactivity.EventRoute.RaiseEventImpl(RoutedEventArgs e) in /_/src/Avalonia.Interactivity/EventRoute.cs:line 148
   at Avalonia.Interactivity.EventRoute.RaiseEvent(IInteractive source, RoutedEventArgs e) in /_/src/Avalonia.Interactivity/EventRoute.cs:line 79
   at Avalonia.Interactivity.Interactive.RaiseEvent(RoutedEventArgs e) in /_/src/Avalonia.Interactivity/Interactive.cs:line 123
   at Avalonia.Input.MouseDevice.MouseUp(IMouseDevice device, UInt64 timestamp, IInputRoot root, Point p, PointerPointProperties props, KeyModifiers inputModifiers) in /_/src/Avalonia.Input/MouseDevice.cs:line 313
   at Avalonia.Input.MouseDevice.ProcessRawEvent(RawPointerEventArgs e) in /_/src/Avalonia.Input/MouseDevice.cs:line 144
   at Avalonia.Input.InputManager.ProcessInput(RawInputEventArgs e) in /_/src/Avalonia.Input/InputManager.cs:line 37
   at Avalonia.RawEventGrouper.DispatchFromQueue() in /_/src/Shared/RawEventGrouping.cs:line 54
   at Avalonia.Threading.JobRunner.RunJobs(Nullable`1 priority) in /_/src/Avalonia.Base/Threading/JobRunner.cs:line 37
   at Avalonia.X11.X11PlatformThreading.HandleX11(CancellationToken cancellationToken) in /_/src/Avalonia.X11/X11PlatformThreading.cs:line 169
   at Avalonia.X11.X11PlatformThreading.RunLoop(CancellationToken cancellationToken) in /_/src/Avalonia.X11/X11PlatformThreading.cs:line 245
   at Avalonia.Threading.Dispatcher.MainLoop(CancellationToken cancellationToken) in /_/src/Avalonia.Base/Threading/Dispatcher.cs:line 65
   at Avalonia.Controls.ApplicationLifetimes.ClassicDesktopStyleApplicationLifetime.Start(String[] args) in /_/src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs:line 120
   at Avalonia.ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime[T](T builder, String[] args, ShutdownMode shutdownMode) in /_/src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs:line 209

Desktop (please complete the following information):

• OS: Linux

[furesoft]

The problem will be fixed in the next major update