Hey guys! WC()->cart is null in 3.6.1 if running in a method callable by a custom REST API route.

Check below code. Why has a _minor_ release led to so many issues?

/**
 * Routes helper
 */
class Routes {
    /**
     * Adds some actions
     */
    public function __construct() {
        add_action( 'rest_api_init', array( $this, 'register' ) );
    }

    /**
     * Registers the routes
     */
    public function register() {
        $namespace = 'nch';
        register_rest_route(
            $namespace,
            '/add_to_cart',
            array(
                array(
                    'methods'             => 'POST',
                    'callback'            => array( $this, 'add_to_cart' ),
                ),
            )
        );
    }

    /**
     * Creates the actual cart
     *
     * @param Any $request The current request.
     */
    public function add_to_cart( $request ) {
        /**
         * [REDACTED]
         */

        // Empty existing cart.
        WC()->cart->empty_cart( true ); // THIS CRASHES IN 3.6.1
        WC()->session->set( 'cart', array() );

        /**
         * [REDACTED]
         */
    }
}