Angular 5.2.0: Cannot read property of undefined in ngZone.run

Question

I'm completely new to Angular, so I hope I can describe my problem clearly. I'm trying to get the date property from an observable to display it in KendoUI datetime picker in frontend.

Here is my source code: I have an object ResultObject with 2 properties (id, myCustomDate). The id property is of type number and the myCustomDate property is of type Date.

I got my data over a REST API request. Here is the call:

this.httpService.get<ResultObject>(this.service.Url + "getresultobject", { blockUi: true }).
    subscribe(result => this.result$.next(result));

//this is where I get the result through a web service call:
result$: Subject<ResultObject> = new BehaviorSubject<ResultObject>(null);

//this is where I create my observable, in the constructor:
this.resultObeservable$ = this.result$.map(r => r);

And here is the main problem which I have, I'm trying to assign a the property date from the object result:

this.resultObeservable$.subscribe(d => this.ngZone.run(() => {
   console.log(d);
   this.myCustomDate= d.resultDate; //----> here i get the exception
}));

The exception says that d is null or undefined.

As I said, I'm totally new to Angular and I even don't know if the usage of ngZone is correct like this. So it would be great if I get any help.