Fix categories loading in side menu component.

frontend/src/app/core/service/category.service.ts

@@ -17,8 +17,8 @@ export class CategoryService {
   get categories$(): Observable<Category[]> {
     if (!this.categories?.length) {
       this.categoryRestService.getCategories()
-      .then(categories => this.categoriesSubject.next(categories))
-      .catch(error => console.error('An error occured while loading categories.', error));
+        .then(categories => this.categoriesSubject.next(categories))
+        .catch(error => console.error('An error occured while loading categories.', error));
     }
     return this.categoriesSubject.asObservable();
   }