message: never create a notification if unit is invisible
diff: @@ -86,7 +86,7 @@ export class NotificationController {
  if (changedCourse && !changedCourse.active) {
  return;
  }
  - if (changedUnit && !changedUnit.visible && changedCourse.active) {
  + if (changedUnit && !changedUnit.visible) {
  return;
  }
  const notification = new Notification();
  