Proper error on creating analytic unit with multiple metrics

src/models/metric.ts

@@ -37,6 +37,9 @@ export class Metric {
 export class MetricExpanded {
   private _targets: Target[];
   constructor(public datasource: string, targets: any[]) {
+    if(targets.length > 1) {
+      throw new Error('Multiple metrics are not supported currently');
+    }
     this._targets = targets.map(t => new Target(t));
   }
 

src/module.ts

@@ -532,11 +532,19 @@ class GraphCtrl extends MetricsPanelCtrl {
 
   async saveNew() {
     this.refresh();
+    try {
       await this.analyticsController.saveNew(
         new MetricExpanded(this.panel.datasource, this.panel.targets),
         this.datasourceRequest,
         this.panel.id
       );
+    } catch(e) {
+      this.alertSrv.set(
+        'Error while saving analytic unit',
+        e.message,
+        'error', 7000
+      );
+    }
     this.$scope.$digest();
     this.render(this.seriesList);
   }