Exception in JobContoller::initializeListAction due to uninitialized array elements

[sypets]

There is an exception when loading a page with the plugin in the FE.

PHP Warning: Undefined array key "filter" in /var/www/dev6.t3.uol.de/htdocs/typo3conf/ext/jobfair/Classes/Controller/JobController.php line 178

• with PHP 8.1
• debug mode / environment
• TYPO3 11.5.30
• jobfair: dev-master