Angular 2 and Firebase - Build an Application

Author: jhades

src/app/shared/model/lessons.service.ts

@@ -63,6 +63,7 @@ export class LessonsService {
                 limitToLast: 2
             }
         })
+        .filter(results => results && results.length > 0)
         .map(results => results[0].$key)
         .switchMap(lessonId => this.db.object(`lessons/${lessonId}`))
         .map(Lesson.fromJson);