E_WARNING: Undefined variable $navClass

[HMJR]

Below the error log after upgrading to Release 2023-04-04 "Jack Jackrum" (template sprintDoc)
$navClass/home////public_html/nl/lib/tpl/sprintdoc/tpl/nav-usertools-buttons.php(6)
#0 /home////public_html/nl/lib/tpl/sprintdoc/tpl/nav-usertools-buttons.php(6): dokuwiki\ErrorHandler::errorHandler()
#1 /home////public_html/nl/lib/tpl/sprintdoc/detail.php(237): include('/home/fp106625/...')
#2 /home////public_html/nl/lib/exe/detail.php(45): include('/home/fp106625/...')
#3 {main}

Thanks for an explanation and tips.
Henk M.