Exception when changing the threshold in a classification threshold view

[gkronber]

Stack trace:

************** Exception Text **************
System.NullReferenceException: Object reference not set to an instance of an object.
   at System.Windows.Forms.DataVisualization.Charting.Chart.get_Annotations()
   at HeuristicLab.Problems.DataAnalysis.Views.DiscriminantFunctionClassificationSolutionThresholdView.AddThresholds() in C:\reps\HeuristicLab\trunk\sources\HeuristicLab.Problems.DataAnalysis.Views\3.4\Classification\DiscriminantFunctionClassificationSolutionThresholdView.cs:line 170
   at HeuristicLab.Problems.DataAnalysis.Views.DiscriminantFunctionClassificationSolutionThresholdView.Model_ThresholdsChanged(Object sender, EventArgs e) in C:\reps\HeuristicLab\trunk\sources\HeuristicLab.Problems.DataAnalysis.Views\3.4\Classification\DiscriminantFunctionClassificationSolutionThresholdView.cs:line 105
   at System.EventHandler.Invoke(Object sender, EventArgs e)
   at HeuristicLab.Problems.DataAnalysis.DiscriminantFunctionClassificationModel.OnThresholdsChanged(EventArgs e) in C:\reps\HeuristicLab\trunk\sources\HeuristicLab.Problems.DataAnalysis\3.4\Implementation\Classification\DiscriminantFunctionClassificationModel.cs:line 138
   at HeuristicLab.Problems.DataAnalysis.DiscriminantFunctionClassificationModel.SetThresholdsAndClassValues(IEnumerable`1 thresholds, IEnumerable`1 classValues) in C:\reps\HeuristicLab\trunk\sources\HeuristicLab.Problems.DataAnalysis\3.4\Implementation\Classification\DiscriminantFunctionClassificationModel.cs:line 105
   at HeuristicLab.Problems.DataAnalysis.Views.DiscriminantFunctionClassificationSolutionThresholdView.chart_AnnotationPositionChanging(Object sender, AnnotationPositionChangingEventArgs e) in C:\reps\HeuristicLab\trunk\sources\HeuristicLab.Problems.DataAnalysis.Views\3.4\Classification\DiscriminantFunctionClassificationSolutionThresholdView.cs:line 285
   at System.Windows.Forms.DataVisualization.Charting.Chart.OnAnnotationPositionChanging(AnnotationPositionChangingEventArgs& args)
   at System.Windows.Forms.DataVisualization.Charting.Annotation.SetPositionRelative(RectangleF position, PointF anchorPoint, Boolean userInput)
   at System.Windows.Forms.DataVisualization.Charting.Annotation.AdjustLocationSize(SizeF movingDistance, ResizingMode resizeMode, Boolean pixelCoord, Boolean userInput)
   at System.Windows.Forms.DataVisualization.Charting.AnnotationCollection.OnMouseMove(MouseEventArgs e)
   at System.Windows.Forms.DataVisualization.Charting.Chart.OnChartMouseMove(MouseEventArgs e)
   at HeuristicLab.Visualization.ChartControlsExtensions.EnhancedChart.OnMouseMove(MouseEventArgs e) in C:\reps\HeuristicLab\trunk\sources\HeuristicLab.Visualization.ChartControlsExtensions\3.3\EnhancedChart.cs:line 142
   at System.Windows.Forms.Control.WmMouseMove(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)