Ionic Login Via Google Plus Problem

In my app I logged in successfully user via google plus… and after i want remember login => i use storage save user…
but a new happen when i logout. my function logout is this.googlePlus.logout() => error because I not logged in before!
Are you help me!

What libraries are you using?

what is your mean? i dont understand

What library does this code use?

Where does this.googlePlus come from?

is use GooglePlus of ionic native: import { GooglePlus } from '@ionic-native/google-plus';

Ok so

Show us the code you used to implement it.

thank you…