fix 'undefined' error on anonymous item page landing

src/app/item-page/edit-item-page/edit-item-page.component.html

@@ -3,7 +3,7 @@
         <div class="col-12">
             <h1 class="border-bottom">{{'item.edit.head' | translate}}</h1>
             <div class="pt-2">
-                <ul class="nav nav-tabs justify-content-start" role="tablist">
+              <ul *ngIf="pages.length > 0" class="nav nav-tabs justify-content-start" role="tablist">
                     <li *ngFor="let page of pages" class="nav-item" role="presentation">
                         <a *ngIf="(page.enabled | async)"
                            [attr.aria-selected]="page.page === currentPage"

src/app/item-page/simple/item-page.component.ts

@@ -2,7 +2,7 @@
 import { ActivatedRoute, Router } from '@angular/router';
 import { isPlatformServer } from '@angular/common';
 
-import { Observable, combineLatest } from 'rxjs';
+import { Observable, combineLatest, of } from 'rxjs';
 import { map, switchMap, take } from 'rxjs/operators';
 
 import { ItemDataService } from '../../core/data/item-data.service';
@@ -155,6 +155,8 @@
       switchMap((coarLdnEnabled: boolean) => {
         if (coarLdnEnabled) {
           return this.notifyInfoService.getCoarLdnLocalInboxUrls();
+        } else {
+          return of([]);
         }
       })
     );