Hide checked field

Hi
I just want to output the second field if the first one is empty but never output the first field. I read here http://drupal.org/node/206012 that this could be achieved by changing

       
        if (empty($fields[$emptyfield]->last_render)) {
          $this->last_render = $fields[$outputfield]->last_render;
        }
        else {
          $this->last_render = $fields[$emptyfield]->last_render;
        }

To

        if (empty($fields[$emptyfield]->last_render)) {
          $this->last_render = $fields[$outputfield]->last_render;
        }
        else {
          $this->last_render = '';
        }

But for me this throws this error

Notice: Undefined property: views_handler_field_field::$last_render in views_ifempty_handler_field->render() (line 114 of /home/smarkit3/public_html/www.intnews.com/TTIBuyersGuide/sites/all/modules/views_ifempty/includes/...).

Is there a possibility of adding this feature or maybe suggest a change to the above code so it doesn't give an error?

Thanks