add support for paginated properties on dspace objects

src/app/shared/loading/loading.component.ts

@@ -3,6 +3,7 @@ import { Component, Input, OnDestroy, OnInit } from '@angular/core';
 import { TranslateService } from '@ngx-translate/core';
 
 import { Subscription } from 'rxjs/Subscription';
+import { hasValue } from '../empty.util';
 
 @Component({
   selector: 'ds-loading',
@@ -28,7 +29,7 @@ export class LoadingComponent implements OnDestroy, OnInit {
   }
 
   ngOnDestroy() {
-    if (this.subscription !== undefined) {
+    if (hasValue(this.subscription)) {
       this.subscription.unsubscribe();
     }
   }