diff --git a/Elwig/Windows/ChartWindow.xaml.cs b/Elwig/Windows/ChartWindow.xaml.cs
index cb827ef..0a4a0f5 100644
--- a/Elwig/Windows/ChartWindow.xaml.cs
+++ b/Elwig/Windows/ChartWindow.xaml.cs
@@ -33,11 +33,25 @@ namespace Elwig.Windows {
         private Marker PrimaryMarkedPointPlot;
         private Marker SecondaryMarkedPointPlot;
         private Text TooltipPlot;
-        private LegendItem UngebundenLegend;
-        private LegendItem GebundenLegend;
-        private LegendItem LdwLegend;
-        private LegendItem QuwLegend;
-        private LegendItem KabLegend;
+
+        private static readonly LegendItem
+            UngebundenLegend = new() {
+                Label = "Ungebunden", LineWidth = 1, LineColor = ColorUngebunden,
+                Marker = new(MarkerShape.FilledCircle, 5, ColorUngebunden)
+            },
+            GebundenLegend = new() {
+                Label = "Gebunden", LineWidth = 1, LineColor = ColorGebunden,
+                Marker = new(MarkerShape.FilledCircle, 5, ColorGebunden)
+            },
+            LdwLegend = new() {
+                Label = "68 °Oe (LDW)", LineWidth = 2, LineColor = Colors.Red, Marker = MarkerStyle.None
+            },
+            QuwLegend = new() {
+                Label = "73 °Oe (QUW)", LineWidth = 2, LineColor = Colors.Orange, Marker = MarkerStyle.None
+            },
+            KabLegend = new() {
+                Label = "84 °Oe (KAB)", LineWidth = 2, LineColor = Colors.Green, Marker = MarkerStyle.None
+            };
 
         private (Graph? Graph, int Index) LastHighlighted = (null, -1);
         private (Graph? Graph, int Index) Highlighted = (null, -1);
@@ -97,10 +111,11 @@ namespace Elwig.Windows {
             GraphEntries.ForEach(e => {
                 e.Vaributes.ForEach(v => {
                     var found = Vaributes.Find(a => a.Attribute?.AttrId == v.Attribute?.AttrId && a.Variety?.SortId == v.Variety?.SortId);
+                    if (found == null) return;
                     if (e.Abgewertet) {
-                        found!.AssignedAbgewGraphId = e.Id;
+                        found.AssignedAbgewGraphId = e.Id;
                     } else {
-                        found!.AssignedGraphId = e.Id;
+                        found.AssignedGraphId = e.Id;
                     }
                 });
             });
@@ -173,41 +188,6 @@ namespace Elwig.Windows {
         }
 
         private void InitPlot() {
-            UngebundenLegend = new LegendItem() {
-                Label = "Ungebunden",
-                LineWidth = 1,
-                LineColor = ColorUngebunden,
-                Marker = new MarkerStyle(MarkerShape.FilledCircle, 5, ColorUngebunden)
-            };
-
-            GebundenLegend = new LegendItem() {
-                Label = "Gebunden",
-                LineWidth = 1,
-                LineColor = ColorGebunden,
-                Marker = new MarkerStyle(MarkerShape.FilledCircle, 5, ColorGebunden)
-            };
-
-            LdwLegend = new LegendItem() {
-                Label = "68 °Oe (LDW)",
-                LineWidth = 2,
-                LineColor = Colors.Red,
-                Marker = MarkerStyle.None
-            };
-
-            QuwLegend = new LegendItem() {
-                Label = "73 °Oe (QUW)",
-                LineWidth = 2,
-                LineColor = Colors.Orange,
-                Marker = MarkerStyle.None
-            };
-
-            KabLegend = new LegendItem() {
-                Label = "84 °Oe (KAB)",
-                LineWidth = 2,
-                LineColor = Colors.Green,
-                Marker = MarkerStyle.None
-            };
-
             RefreshGradationLines();
 
             if (SelectedGraphEntry?.GebundenGraph != null) {