$is_empty_function = $field['module'] .'_content_is_empty';
        if ($is_empty_function($form_state['values'][$field_name][$delta], $field)) {
          // Ignore fields that are not required.
          if (!$field['required']) {
            continue;
          }

          // Build an error message for this field in this subgroup, but do
          // not flag it, yet.
          if (!empty($item['_error_element'])) {
            // Here we don't know the number of elements and subelements a
            // widget could have added to the form, so we need to extract
            // components from the top, where we have group/delta/field, and
            // then push back field/delta on top of the list.
            $error_element = explode('][', $item['_error_element']);
            array_shift($error_element);
            array_shift($error_element);
            array_shift($error_element);
            array_unshift($error_element, $field_name, $delta);
            $error_element = implode('][', $error_element);
          }
          else {
            $error_element = '';
          }
          $required_field_errors[$delta][$field_name] = array(
            'element' => $error_element,
            'message' => t('!name field is required in group group.', array(
              '!name' => $form[$group_name][$delta][$field_name]['#title'],
              'group' => t($group['label']),
            )),
          );
        }