code: @Override
      public JobProperty<?> newInstance(StaplerRequest req, JSONObject formData) throws FormException {
          // JobPropertyDescriptors are bit different in that we allow them even without any user-visible configuration parameter,
          // so replace the lack of form data by an empty one. 
          if(formData.isNullObject()) formData=new JSONObject();
  
          return super.newInstance(req, formData);
      }
docs: {@inheritDoc}
  
  @return
  null to avoid setting an instance of {@link JobProperty} to the target project (or just use {@link OptionalJobProperty})