TypeError:这个_父订阅。取消订阅不是函数

fbLogin.unsubscribe(); 是问题所在,但即使删除了这两行,错误仍然存在。我使用的是rxjs@^5.5.2。

ERROR TypeError: this._parentSubscription.unsubscribe is not a function
    at Subscriber._unsubscribeParentSubscription (Subscriber.js:110)
    at Subscriber.error (Subscriber.js:75)
    at auth.ts:54
    at e.b (auth.esm.js:17)
    at Fb (auth.esm.js:20)
    at Bb (auth.esm.js:20)
    at A.g.Xb (auth.esm.js:19)
    at kb (auth.esm.js:13)
    at t.invoke (polyfills.js:3)
    at Object.onInvoke (core.js:4760)


//login.ts
loginWithFacebook(): void{
        let fbLogin = this.authData.loginWithFacebook().subscribe(() => {
            fbLogin.unsubscribe();
            this.navCtrl.setRoot('HomePage');
        }, error => {
            fbLogin.unsubscribe();
            console.log(error);
        });
    }


//auth.ts
loginWithFacebook(): Observable<any> {
        return Observable.create(observer => {
            if (this.platform.is('cordova')) {
                return this.fb.login(['email', 'public_profile']).then(res => {
                    const facebookCredential = firebase.auth.FacebookAuthProvider.credential(res.authResponse.accessToken);
                    this.afAuth.auth.signInWithCredential(facebookCredential).then(()=> {
                        observer.next();
                    }).catch(error => {
                        console.log(error);
                        observer.error(error);
                    });
                });
            } else {
                return this.afAuth.auth.signInWithPopup(new firebase.auth.FacebookAuthProvider()).then(()=> {
                    observer.next();
                }).catch(error => {
                    console.log(error);
                    observer.error(error); //this is auth.ts:54
                });
            }
        });
    }