Http request inside a http interceptor angular

I need to do a http request inside my interceptor.

I try:

  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    const authToken = localStorage.getItem('token');
    if(authToken != null){
        if(req.url !== AppSettings.API_ENDPOINT + 'plano/busca'){
        let http: HttpClient = this.injector.get(HttpClient);

        const httpOptions = {
            headers: new HttpHeaders({
              'token': authToken,
              'Authorization': 'bearer ' + authToken
            })
          };

        return http.get(AppSettings.API_ENDPOINT + 'plano/busca', httpOptions).pipe(switchMap((response) => {
            console.log(response);
            const newRequest = req.clone({
                setHeaders: { Authorization: `bearer ${authToken}`, token: `${authToken}` }
            });
            return next.handle(newRequest);
        }),
        catchError((err) => {
            console.log(err)
            return Observable.throw(err); 
        }
    )

    );
    }}else {
        return next.handle(req);
        }
    }

but i'm receiving in console:

TypeError: You provided 'undefined' where a stream was expected. You can provide an Observable, Promise, Array, or Iterable. at subscribeTo (subscribeTo.js:41) at subscribeToResult (subscribeToResult.js:6) at MergeMapSubscriber.push../node_modules/rxjs/_esm5/internal/operators/mergeMap.js.MergeMapSubscriber._innerSub (mergeMap.js:70) at MergeMapSubscriber.push../node_modules/rxjs/_esm5/internal/operators/mergeMap.js.MergeMapSubscriber._tryNext (mergeMap.js:67) at MergeMapSubscriber.push../node_modules/rxjs/_esm5/internal/operators/mergeMap.js.MergeMapSubscriber._next (mergeMap.js:50)