Sporadic crash in editor

Hi,

we have received a customer report over sporadic crashes that happen when the editor is opened:

Unhandled Hardware Exception:
System.NullReferenceException: Object reference not set to an instance of an object.
   at ActiproSoftware.Windows.Controls.SyntaxEditor.Primitives.EditorView.LTh()
   at ActiproSoftware.Internal.Efn.DdQ()
   at ActiproSoftware.Internal.Efn.ad6(Object  , Object  )
   at System.Windows.Threading.DispatcherTimer.FireTick(Object unused)
   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, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   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.DispatcherOperation.Wait(TimeSpan timeout)

The method seems to be "OnPointerHoverTimerTick".

I am not really sure what happens here. The only thing I can think of is, that this is a multi-thread issue where "pointerHoverEventArgs" is changed in a different thread. But that does not seem likely. Maybe you have a better idea?

The problem occurs when multiple files are loaded to restore the document layout. So I could imagine that the timer is started when the editor is visible. But by the time the tick event is handled, the editor is no longer visible.

We actually have a couple of services that implement "IEditorViewPointerInputEventSink", but the callback for "NotifyPointerHovered" is always empty. So I don't think they are the problem here.