Fix bug in generic select template

src/app/components/results-chart/chart-type.component.ts

@@ -96,4 +96,9 @@ export class ChartTypeSelectComponent implements IObservable {
     public get enableHelpButton() {
         return false;
     }
+
+    // implemented because of generic template
+    public get messageWhenEmpty(): string {
+        return undefined;
+    }
 }