Fix: Unsubscribe from events in dashboards (#19788)

* Unsubscribe on unmount

* Fix unsubscribe

public/app/features/dashboard/dashgrid/PanelChrome.tsx

@@ -81,6 +81,8 @@ export class PanelChrome extends PureComponent<Props, State> {
 
   componentWillUnmount() {
     this.props.panel.events.off(PanelEvents.refresh, this.onRefresh);
+    this.props.panel.events.off(PanelEvents.render, this.onRender);
+
     if (this.querySubscription) {
       this.querySubscription.unsubscribe();
       this.querySubscription = null;

public/app/features/dashboard/panel_editor/VisualizationTab.tsx

@@ -151,6 +151,9 @@ export class VisualizationTab extends PureComponent<Props, State> {
   }
 
   componentWillUnmount() {
+    if (this.querySubscription) {
+      this.querySubscription.unsubscribe();
+    }
     this.cleanUpAngularOptions();
   }