message: Reenable Download Button if nothing selected
diff: @@ -87,6 +87,7 @@ export class DownloadCourseDialogComponent implements OnInit {
  const obj = await this.buildObject();
  if (obj.lectures.length === 0) {
  this.snackBar.open('No units selected!', 'Dismiss', {duration: 3000});
  + this.disableDownloadButton = false;
  return;
  }
  const downloadObj = <IDownload> obj;
  