Fix get language session on init

Frontend Angular 4/src/app/app.component.ts

@@ -10,7 +10,8 @@ import { TranslateService } from '../../node_modules/@ngx-translate/core';
 export class AppComponent implements OnInit {
     constructor(public router: Router, public translate: TranslateService) {
         this.translate.addLangs(['es', 'en']);
-        let language = JSON.parse(sessionStorage.getItem("currentUser")).language;
+        let currentSession = sessionStorage.getItem("currentUser"); 
+        let language = currentSession ? JSON.parse(currentSession).language : 'es';
         if (language) {
             this.translate.setDefaultLang(language);
         } else {