ArgumentException
   at System.Windows.Documents.TextPointer.InitializeOffset(TextPointer position, Int32 distance, LogicalDirection direction)
   at System.Windows.Documents.TextPointer.System.Windows.Documents.ITextPointer.CreatePointer(Int32 offset, LogicalDirection gravity)
   at System.Windows.Documents.CompositionAdorner.AttributeRange.AddCompositionLines()
   at System.Windows.Documents.CompositionAdorner.InvalidateAdorner()
   at System.Windows.Documents.TextServicesProperty.OnLayoutUpdated()
   at System.Windows.Documents.TextStore.OnLayoutUpdated()
   at System.Windows.Documents.TextEditor.OnTextViewUpdatedWorker(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)