System.NullReferenceException: Object reference not set to an instance of an object.

[beichenyumo123]

Describe the bug
Observing the following error:

System.NullReferenceException: Object reference not set to an instance of an object.
   at FancyWM.TilingService.CanPullUp()
   at FancyWM.MultiDisplayTilingService.CanPullUp()
   at FancyWM.MainWindow.GetAvailableActions()+MoveNext()
   at System.Collections.Generic.HashSet`1.UnionWith(IEnumerable`1 other)
   at System.Collections.Generic.HashSet`1..ctor(IEnumerable`1 collection, IEqualityComparer`1 comparer)
   at System.Linq.Enumerable.ToHashSet[TSource](IEnumerable`1 source, IEqualityComparer`1 comparer)
   at System.Linq.Enumerable.ToHashSet[TSource](IEnumerable`1 source)
   at FancyWM.MainWindow.GetContextHintsExtraContent()
   at FancyWM.MainWindow.ShowWaitingForActionToast(Boolean showContextHints, CancellationToken cancellationToken)
   at FancyWM.MainWindow.<>c__DisplayClass67_1.<<OnCmdSequenceBegin>b__1>d.MoveNext()
--- End of stack trace from previous location ---
   at FancyWM.Utilities.Dispatchers.<>c__DisplayClass4_0.<RethrowOnDispatcher>b__0()
   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 System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Windows.Threading.DispatcherOperation.Invoke()
   at System.Windows.Threading.Dispatcher.ProcessQueue()
   at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   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 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.Application.RunDispatcher(Object ignore)
   at System.Windows.Application.RunInternal(Window window)
   at FancyWM.Startup.AppMain(String[] args)
   at FancyWM.Startup.Main(String[] args)
   at FancyWM.GUI.Program.Main(String[] args)

To Reproduce
Steps to reproduce the behavior:

1. Open '...'
2. Resize '....'
3. Enable '....'
4. See error

Expected behavior
A clear and concise description of what you expected to happen.

Desktop (please complete the following information):

• OS: Microsoft Windows NT 10.0.26200.0
• FancyWM Version: 2.19.0.0

Additional context
Add any other context about the problem here.