   // Even the dom-if has checked the exception is not null, it only
      // prevents the rendering at first time. When switching to a job with
      // exception and back, it just change the dom to hide, which triggers
      // the binded function and throw exception. So null check is still needed
      // in these functions.
      exceptionMessage(exception) {
        if (!exception) {
          return '';
        }
        return exception.message;
      },

      exceptionTraceback(exception) {
       