How to fix
Locate the line in the admin/applications/core/modules_admin/diagnostics/diagnostics.php file:
'sql_driver' => strtoupper(SQL_DRIVER),
Replace it with:
'sql_driver' => strtoupper(IPSSetUp::getSavedData('sql_driver')),
Add the following line at the beginning of the _listFunctions() method:
require_once(IPS_ROOT_PATH . '/setup/sources/base/setup.php');