use y1/y2 axis definitions

pdb-js/src/app/visualization-page/visualization-page.component.ts

@@ -49,6 +49,7 @@ export class VisualizationPageComponent implements OnInit {
     
   enableGallery = false;
   splitBy = null;
+  y2AxisAvailable = false;
 
   constructor(private plotService: PlotService, private snackBar: MatSnackBar) {
   }
@@ -83,6 +84,9 @@ export class VisualizationPageComponent implements OnInit {
     const compatiblePlotTypes = this.plotTypes.filter(pt => pt.compatible(selectedPlotTypes));
     this.plotTypes.forEach(pt => pt.active=false);
     compatiblePlotTypes.forEach(pt => pt.active=true);
+    
+    const axesTypes = this.getAxes();
+    this.y2AxisAvailable = axesTypes.y.length == 2;
   }
    
   
@@ -144,7 +148,7 @@ export class VisualizationPageComponent implements OnInit {
     this.selectedPlotType.forEach(a => aggregates.push(a.id));
     
     const y1 = this.y1AxisDefinitionComponent.getAxisDefinition();
-    const y2 = this.y2AxisDefinitionComponent.getAxisDefinition();
+    const y2 = this.y2AxisDefinitionComponent ? this.y2AxisDefinitionComponent.getAxisDefinition() : undefined;
     
     const request = new PlotRequest();
     request.query = this.query.query;