case 'process form values':
        if ($field['multiple']) {
          // if nothing selected, make it 'none'
          if (empty($items['nids'])) {
            $items['nids'] = array(0 => '0');
          }
          // drop the 'none' options if other items were also selected
          elseif (count($items['nids']) > 1) {
            unset($items['nids'][0]);
          }

          $items = array_values(content_transpose_array_rows_cols(array('nid' => $items['nids'])));
        }
        else {
          $items[0]['nid'] = $items['nids'];
        }
        // Remove the widget's data representation so it isn't saved.
        unset($items['nids']);
        foreach ($items as $delta => $item) {
          $items[$delta]['error_field'] =  $field['field_name'] .'][nids';
        }