Fix unused variable in app.component.ts

frontend/src/app/_services/locationBack.service.ts

@@ -8,7 +8,9 @@ import { Router, NavigationEnd } from '@angular/router'
 export class LocationBackService {
   private history: string[] = [];
 
-  constructor(private router: Router, private location: Location) {
+  constructor(private router: Router, private location: Location) { }
+
+  initialize() {
     this.router.events.subscribe((event) => {
       if (event instanceof NavigationEnd && !event.urlAfterRedirects.includes('login')) {
         this.history.push(event.urlAfterRedirects);

frontend/src/app/app.component.ts

@@ -32,6 +32,7 @@ export class AppComponent {
     public guard: AuthorizeGuard
   ) {
     this.revision_datetime_string = new Date(versions.revision_timestamp).toLocaleString(undefined,  { day: '2-digit', month: '2-digit', year: 'numeric', hour: 'numeric', minute: 'numeric', second: 'numeric' });
+    this.locationBackService.initialize();
   }
 
   loadAlerts() {