I installed WordPress with Embark theme and Calindarista plugin about a year. Now with the new WordPress 6.7.1 update I get the below error. I tried to update Calendarista from 15.0.4 to 16.0.6, but it fails. I updated all the plugins, except Calendarista, but the same error appears.

What could be the problem?

The log:

Fatal error: Uncaught Error: Call to a member function get() on null in /home/atvmotot/public_html/wp-content/plugins/calendarista/lib/infrastructure/utils/WooCommerceHelper.php:139 Stack trace: #0 /home/atvmotot/public_html/wp-includes/class-wp-hook.php(324): Calendarista_WooCommerceHelper::customCheckoutFields(NULL, ‘billing_country’) #1 /home/atvmotot/public_html/wp-includes/plugin.php(205): WP_Hook->apply_filters(NULL, Array) #2 /home/atvmotot/public_html/wp-content/plugins/woocommerce/includes/class-wc-checkout.php(1364): apply_filters(‘woocommerce_che…’, NULL, ‘billing_country’) #3 /home/atvmotot/public_html/wp-content/plugins/woocommerce/includes/class-wc-checkout.php(231): WC_Checkout->get_value(‘billing_country’) #4 /home/atvmotot/public_html/wp-content/plugins/woocommerce/includes/class-wc-checkout.php(321): WC_Checkout->initialize_checkout_fields() #5 /home/atvmotot/public_html/wp-content/plugins/woocommerce-gateway-stripe/includes/payment-methods/class-wc-stripe-upe-payment-gateway.php(384): WC_Checkout->get in /home/atvmotot/public_html/wp-content/plugins/calendarista/lib/infrastructure/utils/WooCommerceHelper.php on line 139

The entire log file: https://pastebin.com/vWKMgNNh

In the function.php I have:

 __( 'Disponibilitate', 'woocommerce' ),
        'priority'  => 10,
        'callback'  => 'woo_new_product_tab_content'
    );
    return $tabs;
}
function woo_new_product_tab_content() {
    echo '
Calendar Disponibilitate
';
    echo '
' . do_shortcode("[calendarista-public-calendar id=\"5\" view=\"week\" status=\"1\" availability-name=\"true\"]") . '
';
}
//26.01.2023 custom email name FROM
// Change sender name
function change_default_sender_name( $original_email_from ) {
    return 'ATVMOTOTRAVELER';
}
// Hooking up functions to the correct WordPress filters 
add_filter( 'wp_mail_from_name', 'change_default_sender_name' );

Tried:

1. I tried to update Calendarista from 15.0.4 to 16.0.6, but fails.
2. All plugins updated, except Calendarista
3. Reinstalled WordPress 6.7.1

Expect:

Working edit for Pages.