angular 4 cannot read property 'id' of undefined

Question

i'm trying to use angular 4 to call to a dummy web api, here is my component

export class AppComponent {
    title = 'app';
    url = 'https://api.ipify.org/?format=json';
    results: any;

    constructor(private http: Http) {
        this.getData().subscribe(data => {
            this.results = data.json();
        })
    }

    getData() {
        return this.http.get(this.url);
    }

}

but when i try to display it i get the result but also a screen of error

ERROR TypeError: Cannot read property 'ip' of undefined

what i want to understand is why it is shown because after a split second the data is well displayed .