隐藏ion-nav-back-button的文字

<ion-nav-bar class="bar-positive">
    <ion-nav-back-button>
    </ion-nav-back-button>
</ion-nav-bar>
......

app.config(function ($stateProvider,$ionicConfigProvider) {
        $ionicConfigProvider.backButton.text("");
        $ionicConfigProvider.backButton.previousTitleText(false);
        $stateProvider
                .state('home',{
                    templateUrl:'home.html'
                })
                .state('music',{
                    templateUrl:'music.html'
                });
    });

红色代码可以将ion-nav-back-button中的文本隐藏