Field data from UI not saving as tablefield_field_is_empty() mistakenly returns TRUE

function tablefield_field_is_empty($item, $field) {
...
$count_rows = $item['tablefield']['rebuild']['count_rows'];
...
}

content of $item

tested on form submit. As result field treated empty and $items array of tablefield_field_presave($entity_type, $entity, $field, $instance, $langcode, &$items) is empty and nothing is saving

Notice: Undefined index: rebuild in tablefield_field_is_empty() (line 486 of /var/www/extranet/sites/all/modules/tablefield/tablefield.module).

Drupal core - 7.58

What should be

  $count_rows = 0;
  if(isset($item['tablefield']['rebuild'])) {
    $count_rows = $item['tablefield']['rebuild']['count_rows'];
  } else {
    $count_rows = count($item['tablefield']['tabledata']);
  }