message: Disabled downloadbutton if course is empty
diff: @@ -37,6 +37,9 @@ export class DownloadCourseDialogComponent implements OnInit {
  this.disableDownloadButton = false;
  this.course = this.data.course;
  this.chkbox = true;
  + if (!this.course.lectures.length) {
  + this.disableDownloadButton = true;
  + }
  }
  onChange() {
  