Warning: Undefined variable $warning

Hello. I reinstalled the plugin. When I create a new page, the error message appears very briefly: Warning: Undefined variable $warning in /srv/www/wiesenmarkt/public/wiesenmarktwp/wp-content/plugins/myticket-events/inc/class-woocommerce.php on line 230When I try to save this page I keep getting ERR_CONNECTION_TIMED_OUT. After 5 minutes I get back to the backend, but the error in line 230 keeps coming back. Can you help me? thank you in advance