Fatal error: Uncaught TypeError: array_keys(): Argument #1 ($array) must be of type array, null given in /home/clickboo/public_html/lernkaertchen.ch/lib/src/Model/Karten.php:232 Stack trace: #0 /home/clickboo/public_html/lernkaertchen.ch/lib/src/Model/Karten.php(232): array_keys(NULL) #1 /home/clickboo/public_html/lernkaertchen.ch/lib/src/Controller/Frontend.php(414): Aisberg\Model\Karten::filterGelernteKarten(Array, NULL) #2 /home/clickboo/public_html/lernkaertchen.ch/lib/src/Bootstrap.php(245): Aisberg\Controller\Frontend->indexAction(Array) #3 /home/clickboo/public_html/lernkaertchen.ch/index.php(14): Aisberg\Bootstrap->run() #4 {main} thrown in /home/clickboo/public_html/lernkaertchen.ch/lib/src/Model/Karten.php on line 232