TypeError: Cannot read property 'isUp' of undefined #398 (#416)

src/panel/graph_panel/graph_ctrl.ts

@@ -338,12 +338,22 @@ class GraphCtrl extends MetricsPanelCtrl {
       this._analyticUnitsToShow
     );
 
+    if(this.analyticService === undefined) {
+      appEvents.emit(
+        'alert-error',
+        [
+          'Select Hastic datasource',
+          'Panel config -> Visualization'
+        ]
+      );
+    } else {
       if(this.analyticService.isUp) {
         await this.analyticsController.init();
 
         this._updatePanelInfo();
         this.analyticsController.updateServerInfo();
       }
+    }
 
     this._graphRenderer = new GraphRenderer(
       this.$graphElem, this.timeSrv, this.contextSrv, this.$scope, this.analyticsController