no menu error 500 after upgrade to 5.8.x
Andy, Welcome to CiviCRM stack exchange.

This is a weird error, since this function is already present in CiviCRM 5.8.1. But to trace the problem I would 


Check if the function quicksearchOptions() exists in civicrm/CRM/Core/SelectValues.php.
Check if this file is being over-ridden by any of the extension or custom php
Check if civicrm/CRM/Core/SelectValues.php file is being invoked.


HTH

Pradeep