Fatal: Call to get_cart() on null in Cart.php — check_cart_items() and 2 other methods do not null-check WC()->cart

[officialsyntec]

Summary

Several methods in includes/Cart.php call WC()->cart->get_cart() without checking whether WC()->cart is null. When the woocommerce_check_cart_items action (or add-to-cart validation) fires in a request context where WooCommerce has not initialised the cart, the plugin throws an uncaught fatal and takes down the page for the visitor.

Error

PHP Fatal error: Uncaught Error: Call to a member function get_cart() on null
in .../plugins/wc-min-max-quantities/includes/Cart.php:328
#0 wp-includes/class-wp-hook.php(341): WooCommerceMinMaxQuantities\Cart::check_cart_items()
...
plugin.php(522): do_action('woocommerce_check_cart_items')

Affected code (current master, 2.3.0)

check_cart_items(), add_to_cart_validation() and set_cart_quantity() each iterate the cart with no guard against a null cart object:

foreach ( WC()->cart->get_cart() as $item ) { ... }

Why WC()->cart can be null

WC()->cart is only initialised in front-end cart contexts; it is null in REST API and other optimised/early loads — long-standing WooCommerce behaviour (see woocommerce/woocommerce#23792, #23758, #27157). Any code that triggers woocommerce_check_cart_items outside a normal cart context — for example a floating-cart plugin rendering on wp_footer — reliably hits this and fatals.

Steps to reproduce

WC()->cart = null;
do_action( 'woocommerce_check_cart_items' ); // -> Fatal in check_cart_items()

Environment

• Min Max Quantities 2.3.0
• WooCommerce 10.9.1
• WordPress 6.9
• PHP 8.3

Suggested fix

Add a null guard at the top of each method that dereferences WC()->cart:

if ( is_null( WC()->cart ) ) {
    return; // for the add_to_cart_validation filter: `return $pass;`
}

Happy to open a PR with the guards if that helps.