Fatal Error with PHP 8.1.12

Hi there,
I got the following fatal error:

Error-Details
==============
Ein Fehler vom Typ E_ERROR wurde in der Zeile 259 der Datei /wp-content/plugins/my-calendar/my-calendar-templating.php verursacht. Fehlermeldung: Uncaught TypeError: ksort(): Argument #1 ($array) must be of type array, bool given in /wp-content/plugins/my-calendar/my-calendar-templating.php:259
Stack trace:
#0 /wp-content/plugins/my-calendar/my-calendar-templating.php(259): ksort()
#1 /wp-content/plugins/my-calendar/my-calendar-design.php(55): mc_templates_edit()
#2 /wp-includes/class-wp-hook.php(308): my_calendar_design()
#3 /wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters()
#4 /wp-includes/plugin.php(517): WP_Hook->do_action()
#5 /wp-admin/admin.php(259): do_action()
#6 {main}
thrown`

All the best :).