Unexpected end of JSON input Angular 2(4) http get request

Here is the deal: I have a RESTapi on ASP.NET Core Web Api Server. When i'm trying to get data in Postman, there I do a http post request to controller like this http://localhost:5000/api/account/login with data(username, password) after that simply getting http get request and get data from sql server. I Understand that back-end server is all right. But I also have front-end side on Angular 2. I created a login component where input the info (i.e. username and password) on login page. So when I input info, angular take this, send me StatusCode 200 and navigate me to next page where I'm trying to do http get request to main data in the database through RESTapi. So when angular navigated me to the page with Main Data, it just throws 2 errors:
1)GET http://localhost:5000/Account/Login?ReturnUrl=%2Fapi%2Fwork 404 (Not Found)
2)Unexpected end of JSON input
Though in the Postman I'm simply getting Main Data after post request.
Here's piece of code from data.service.ts where all post and get method located:

getWorks(): Observable<IWork[]>{
        let headers = new Headers();
        headers.append('Content-Type', 'application/json');
        return this.http.get(this._baseUrl + 'work')
            .map((result: Response) => {
                return result.json(); })
        .catch(this.handleError);
    }   



login(user : User) {
        let headers = new Headers();
        headers.append('Content-Type', 'application/json');
        return this.http.post(this._baseUrl + 'account/login', JSON.stringify(user), { headers: headers })
            .map((result: Response) => {
                return result.json();
            }).catch(this.handleError);
    }

Function when user's authorizing in login.component.ts

login() : void {
        let _authenticationResult: OperationResult = new OperationResult(true, '');
        this.dataService.login(this._user).subscribe((result: any) => {
            _authenticationResult.succeeded = result.succeeded;
            _authenticationResult.message = result.message;

            if(_authenticationResult.succeeded) {

                this.notificationService.printSuccessMessage('Welcome ' + this._user.username + '!');
                localStorage.setItem('user', JSON.stringify(this._user));
                this.router.navigate(['/list']);
                return result.status = "200"; 
            } else {
                this.notificationService.printErrorMessage(_authenticationResult.message);
            }
        }),
        error => console.error('Error: ' + error);
    }

And getting Main Data file list-work.component.ts

getData() {
        this.dataService.getWorks().subscribe(result => {
            this.works = result;
            this.subscribeToData();
        }, error => { 
            this.notificationService.printErrorMessage('Authentication reqired');
            this.utilityService.navigateToSignIn();
            console.error('Error: '+ error); });
    }

If it'll helpful here's piece of code from WebApi(.net core) where i retrieve data, but i think deal is not here, cause it's all working on Postman

[Authorize(Policy = "AdminOnly")]
    public async Task<IActionResult> Get()
    {
        if (await _authorizationService.AuthorizeAsync(User, "AdminOnly"))
        {
            IEnumerable<Work> _works = _workRepository
            .AllIncluding(c => c.Creator, t => t.Type, time => time.Time, s => s.Stage)
            .OrderBy(x => x.Id)
            .ToList();
            IEnumerable<WorkViewModel> _workVM = Mapper.Map<IEnumerable<Work>, IEnumerable<WorkViewModel>>(_works);

            return new OkObjectResult(_workVM);
        }
        else
        {
            StatusCodeResult _codeResult = new StatusCodeResult(401);
            return new ObjectResult(_codeResult);
        }
    }

Appriciate any help. Thanks!
Update 1(thanks for NotBad4U):

export class MyBaseRequestsOptions extends BaseRequestOptions { 
  headers: Headers = new Headers({ 'X-Requested-With': 'XMLHttpRequest' }); 
  withCredentials: any = true; 
}
export class DataService extends MyBaseRequestsOptions{
login(user : any) {
        let headers = new Headers();
        headers.append('Content-Type', 'application/json');

        return this.http.post(this._baseUrl + 'account/login', JSON.parse(JSON.stringify(user)), { headers: headers })
            .map((result: Response) => {
                return result.json();
            }).catch(this.handleError);
    }
getWorks(): Observable<IWork[]>{
        let headers = new Headers();
        headers.append('Content-Type', 'application/json');
        return this.http.get(this._baseUrl + 'work' ,{ headers: headers })
            .map((result: Response) => {
                return console.log(result);
                 })
        .catch(this.handleError);
    }