Accept that capabilities API may return an elements: undefined result

frontend/src/app/core/apiv3/cache/cachable-apiv3-collection.ts

@@ -60,7 +60,7 @@ export abstract class CachableAPIV3Collection<
       tap(
         (response:R) => {
           if (response instanceof CollectionResource) {
-            response.elements.forEach(this.touch.bind(this));
+            response.elements?.forEach(this.touch.bind(this));
           } else if (response instanceof HalResource) {
             this.touch(response as any);
           }

frontend/src/app/core/current-user/current-user.service.ts

@@ -124,6 +124,8 @@ export class CurrentUserService {
             // The current page is the only page, return the results.
             return of(data.elements);
           }),
+          // Elements may incorrectly be undefined here due to the way the representer works
+          map((elements) => elements || []),
         )
         .subscribe((capabilities) => {
           this.currentUserStore.update((state) => ({