PROBLEM php8

[df8oe]

Hi,
my server now can run php8. It seems that gs 3.3.16 does work, but there are errors thrown on some pages that uses extended i18n navigation themes. All errors seem to point to i18n:

Fatal error: Uncaught TypeError: count(): Argument #1 ($var) must be of type Countable|array, null given in /var/www/gs3.3.16/plugins/i18n_navigation/frontend.class.php:219 Stack trace:

#0 /var/www/gs3.3.16/plugins/i18n_navigation/frontend.class.php(176): I18nNavigationFrontend::getMenuImpl(Array, 'philosophie', NULL, 100, 5)

#1 /var/www/gs3.3.16/plugins/i18n_navigation/frontend.class.php(259): I18nNavigationFrontend::getMenu('philosophie', 0, 99, 5)

#2 /var/www/gs3.3.16/plugins/i18n_navigation.php(163): I18nNavigationFrontend::outputMenu('philosophie', 0, 99, 5, NULL)

#3 /var/kunden/htdocs/selbst/df8oe/theme/andreas00/template.php(26):get_i18n_navigation(Object(SimpleXMLExtended), 0, 99, 5)

#4 /var/www/gs3.3.16/index.php(134): include('/var/customers/htd...')

#5 {main} thrown in /var/www/gs3.3.16/plugins/i18n_navigation/frontend.class.php on line 219

Pages run on php 7.4 but show error message when I enable debug mode:

Warning: count(): Parameter must be an array or an object that implements Countable in /var/www/gs3.3.16/plugins/i18n_navigation/frontend.class.php on line 219

Any ideas how to fix that?