Crash while splitting windows on vertical monitor

[coremedic]

Describe the bug
On certain applications (Discord, Spotify), when clicking the split button on a vertical monitor FancyWM crashes.

To Reproduce
Steps to reproduce the behavior:

1. Open Discord and Spotify on a vertical monitor
2. Click the split button
3. See error

Expected behavior
No crash, the windows are split

Desktop (please complete the following information):

• OS: Windows 10 Enterprise N LTSC
• OS Build: 19044.4170
• FancyWM Version: 2.11.2.0

Additional context
Error log:

System.NullReferenceException: Object reference not set to an instance of an object.
   at FancyWM.TilingService.OnBeginVerticalWithRequested(Object sender, WindowNode e)
   at FancyWM.TilingOverlayRenderer.WindowViewModel_BeginVerticalSplitWith(Object sender, RoutedEventArgs e)
   at FancyWM.ViewModels.TilingWindowViewModel.<.ctor>b__62_1(Object _)
   at FancyWM.ViewModels.DelegateCommand.Execute(Object parameter)
   at FancyWM.Controls.TilingWindow.OnVerticalSplitMouseMove(Object sender, MouseEventArgs e)
   at System.Windows.Input.MouseEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   at System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
   at System.Windows.Input.InputManager.ProcessStagingArea()
   at System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
   at System.Windows.Input.MouseDevice.Synchronize()
   at System.Windows.Input.InputManager.HitTestInvalidatedAsyncCallback(Object arg)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
   at System.Windows.Threading.DispatcherOperation.InvokeImpl()
   at MS.Internal.CulturePreservingExecutionContext.CallbackWrapper(Object obj)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location ---
   at MS.Internal.CulturePreservingExecutionContext.Run(CulturePreservingExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Windows.Threading.DispatcherOperation.Invoke()
   at System.Windows.Threading.Dispatcher.ProcessQueue()
   at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
   at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
   at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
   at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame)
   at System.Windows.Threading.Dispatcher.Run()
   at System.Windows.Application.RunDispatcher(Object ignore)
   at System.Windows.Application.RunInternal(Window window)
   at System.Windows.Application.Run()
   at FancyWM.Startup.Main(String[] args)