Tengo un error de tiempo de ejecución:

Error al ejecutar 'abrir' en 'XMLHttpRequest': Error de URL no válida: Error al ejecutar 'abrir' en 'XMLHttpRequest': URL no válida en http://localhost:8100/build/polyfills.js:3:2793 en XMLHttpRequest.open (evaluación en s ( http://localhost:8100/build/polyfills.js:2:29793 ), :3:31)

 import { Injectable } from '@angular/core'; import { Http, Headers } from '@angular/http'; import 'rxjs/add/operator/map'; @Injectable() export class Reviews { data: any; constructor(public http: Http) { this.data = null; } getReviews(){ if (this.data) { return Promise.resolve(this.data); } return new Promise(resolve => { this.http.get('http://localhost:app/api/reviews') .map(res => res.json()) .subscribe(data => { this.data = data; resolve(this.data); }); }); } createReview(review){ let headers = new Headers(); headers.append('Content-Type', 'application/json'); this.http.post('http://localhost:app/api/reviews', JSON.stringify(review), {headers: headers}) .subscribe(res => { console.log(res.json()); }); } deleteReview(id){ this.http.delete('http://localhost:app/api/reviews/' + id).subscribe((res) => { console.log(res.json()); }); } }