Fixed errors after upgrade to angular 7

src/app/submission/submission.service.ts

@@ -3,14 +3,7 @@ import { HttpHeaders } from '@angular/common/http';
 import { Router } from '@angular/router';
 
 import { Observable, of as observableOf, Subscription, timer as observableTimer } from 'rxjs';
-import {
-  catchError, concatMap,
-  distinctUntilChanged,
-  filter,
-  find,
-  map,
-  startWith, take, tap
-} from 'rxjs/operators';
+import { catchError, concatMap, distinctUntilChanged, filter, find, map, startWith, take, tap } from 'rxjs/operators';
 import { Store } from '@ngrx/store';
 import { TranslateService } from '@ngx-translate/core';
 
@@ -50,11 +43,7 @@ import { WorkspaceitemSectionsObject } from '../core/submission/models/workspace
 import { RemoteData } from '../core/data/remote-data';
 import { ErrorResponse } from '../core/cache/response.models';
 import { RemoteDataError } from '../core/data/remote-data-error';
-import {
-  createFailedRemoteDataObject$,
-  createSuccessfulRemoteDataObject,
-  createSuccessfulRemoteDataObject$
-} from '../shared/testing/utils';
+import { createFailedRemoteDataObject$, createSuccessfulRemoteDataObject } from '../shared/testing/utils';
 import { SearchService } from '../+search-page/search-service/search.service';
 import { RequestService } from '../core/data/request.service';
 
@@ -117,8 +106,8 @@ export class SubmissionService {
    */
   createSubmission(): Observable<SubmissionObject> {
     return this.restService.postToEndpoint('workspaceitems', {}).pipe(
-      map((workspaceitem: SubmissionObject) => workspaceitem[0]),
-      catchError(() => observableOf({})))
+      map((workspaceitem: SubmissionObject[]) => workspaceitem[0] as SubmissionObject),
+      catchError(() => observableOf({} as SubmissionObject)))
   }
 
   /**