注销用户后引发AngularFire2错误

无法在第行读取null的属性“uid”

这是 uid ngOnInit

ngOnInit() {
    this.authSub1 = this.auth.authState.subscribe((auth) => {
        this.tasksSub = this.af.list(`users/${auth.uid}/tasks`, { preserveSnapshot: true }).subscribe(snapshots => {
            snapshots.forEach(snapshot => {
                this.tasksArray.push(snapshot.val().name);
            });
        });
    }, (err) => {this.openSnackBar(); console.log(err); });
}

然后我打电话 unsbuscribe 在上述订阅上,以避免在 ngOnDestroy 方法:

ngOnDestroy() {
    this.authSub1.unsubscribe();
}

以下是由位于主组件上的按钮触发的注销方法(主组件的路由器出口显示上述组件):

logout() {
    this.auth.auth.signOut()
    .then(() => { 
        this.router.navigateByUrl('/login'); 
    })
    .catch(function(err) {console.log(err); });
}