client crashes if stored credentials cannot be decrypted

[Xkeeper0]

steps to reproduce:

• Have a settings.json stored at ...\AppData\Roaming\Tgstation.Server.ControlPanel
• Attempt to start client
• If settings.json is from a different installation or otherwise cannot be decoded, application crashes at boot

Deleting settings.json provides a workaround but you lose your settings.

In this case the settings.json was from a previous installation of Windows and was carried over.

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
 ---> Internal.Cryptography.CryptoThrowHelper+WindowsCryptographicException: Key not valid for use in specified state.
   at System.Security.Cryptography.ProtectedData.ProtectOrUnprotect(Byte[] inputData, Byte[] optionalEntropy, DataProtectionScope scope, Boolean protect)
   at System.Security.Cryptography.ProtectedData.Unprotect(Byte[] encryptedData, Byte[] optionalEntropy, DataProtectionScope scope)
   at Tgstation.Server.ControlPanel.Models.Credentials.Decrypt() in S:\workspace\Tgstation.Server.ControlPanel\src\Tgstation.Server.ControlPanel\Models\Credentials.cs:line 65
   at Tgstation.Server.ControlPanel.Models.Credentials.get_Password() in S:\workspace\Tgstation.Server.ControlPanel\src\Tgstation.Server.ControlPanel\Models\Credentials.cs:line 18
   at Tgstation.Server.ControlPanel.ViewModels.MainWindowViewModel.get_GitHubToken() in S:\workspace\Tgstation.Server.ControlPanel\src\Tgstation.Server.ControlPanel\ViewModels\MainWindowViewModel.cs:line 104
   at Tgstation.Server.ControlPanel.ViewModels.MainWindowViewModel.UpdateGitHubClient() in S:\workspace\Tgstation.Server.ControlPanel\src\Tgstation.Server.ControlPanel\ViewModels\MainWindowViewModel.cs:line 192
   at Tgstation.Server.ControlPanel.ViewModels.MainWindowViewModel..ctor(IUpdater updater) in S:\workspace\Tgstation.Server.ControlPanel\src\Tgstation.Server.ControlPanel\ViewModels\MainWindowViewModel.cs:line 164
   at Tgstation.Server.ControlPanel.App..ctor() in S:\workspace\Tgstation.Server.ControlPanel\src\Tgstation.Server.ControlPanel\App.xaml.cs:line 17
   --- End of inner exception stack trace ---
   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean wrapExceptions, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& hasNoDefaultCtor)
   at System.RuntimeType.CreateInstanceDefaultCtorSlow(Boolean publicOnly, Boolean wrapExceptions, Boolean fillCache)
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, Boolean wrapExceptions)
   at System.Activator.CreateInstance[T]()
   at Avalonia.Controls.AppBuilderBase`1.<>c__45`1.<Configure>b__45_0() in /_/src/Avalonia.Controls/AppBuilderBase.cs:line 87
   at Avalonia.Controls.AppBuilderBase`1.Setup() in /_/src/Avalonia.Controls/AppBuilderBase.cs:line 306
   at Avalonia.Controls.AppBuilderBase`1.SetupWithLifetime(IApplicationLifetime lifetime) in /_/src/Avalonia.Controls/AppBuilderBase.cs:line 179
   at Avalonia.ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime[T](T builder, String[] args, ShutdownMode shutdownMode) in /_/src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs:line 174
   at Tgstation.Server.ControlPanel.Program.Main(String[] args) in S:\workspace\Tgstation.Server.ControlPanel\src\Tgstation.Server.ControlPanel\Program.cs:line 17