hello, i'have this error on my website:

Fatal error: Uncaught Error: Call to a member function get_list_item_separator() on null in /web/htdocs/www.pierpaoloaiello.com/home/wp-includes/l10n.php:1786 Stack trace: #0 /web/htdocs/www.pierpaoloaiello.com/home/wp-includes/class-wp-theme.php(936): wp_get_list_item_separator() #1 /web/htdocs/www.pierpaoloaiello.com/home/wp-includes/class-wp-theme.php(836): WP_Theme->markup_header() #2 /web/htdocs/www.pierpaoloaiello.com/home/wp-content/plugins/bakery-options/options.php(67): WP_Theme->display() #3 /web/htdocs/www.pierpaoloaiello.com/home/wp-content/plugins/bakery-options/options.php(34): Redux_Framework_Bakery_Options->setSections() #4 /web/htdocs/www.pierpaoloaiello.com/home/wp-includes/class-wp-hook.php(307): Redux_Framework_Bakery_Options->initSettings() #5 /web/htdocs/www.pierpaoloaiello.com/home/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters() #6 /web/htdocs/www.pierpaoloaiello.com/home/wp-includes/plugin.php(476): WP_Hook->do_action() #7 /web/htdocs/www.pierpaoloaiello.com/home/wp-settings.php(461): in /web/htdocs/www.pierpaoloaiello.com/home/wp-includes/l10n.php on line 1786