For running J!5.1 you must https://fabrikar.com/forums/index.php?wiki/update-from-github/ or include the new file manually https://fabrikar.com/forums/index.php?threads/joomla-5-1-and-fabrik-cannot-find-files-error.54473/post-285151 See also Announcements
Please see our announcement here.
$db =& JFactory::getDBO();
$db->setQuery("SELECT labelname FROM labeltable WHERE id = '{tablename__dropdownname_raw}'");
return $db->loadResult();