$wc->cart->set_quantity() error

Hi!
I am trying to programmatically change the quantity of a particular product in the shopping cart after the buyer has met several conditions, but I get a critical error.

} elseif ( $gift_quantity < $current_gift_qt ) { $woocommerce->cart->set_quantity( $giftID, $gift_quantity );
}

After calling this code, Fatal Error appears on the page, and in the log file there is such an entry:

[26-Jun-2023 07:19:24 UTC] PHP Fatal error: Uncaught Error: Call to a member function get_tax_class() on null in /var/www/html/wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php:225
Stack trace:

0 /var/www/html/wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php(651): WC_Cart_Totals->get_items_from_cart()

1 /var/www/html/wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php(143): WC_Cart_Totals->calculate_item_totals()

2 /var/www/html/wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php(134): WC_Cart_Totals->calculate()

3 /var/www/html/wp-content/plugins/woocommerce/includes/class-wc-cart.php(1401): WC_Cart_Totals->__construct(Object(WC_Cart))

4 /var/www/html/wp-content/plugins/woocommerce/includes/class-wc-cart.php(1360): WC_Cart->calculate_totals()

5 /var/www/html/wp-content/themes/niko-theme/functions.php(813): WC_Cart->set_quantity('499924', 2.0)

6 /var/www/html/wp-includes/class-wp-hook.php(308): add_or_remove_gift_from_cart('')

7 /var/www/html/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters('', Array)

8 /var/www/html/wp-includes/plugin.php(517): WP_Hook->do_action(Array)

9 /var/www/html/wp-content/plugins/woocommerce/includes/class-wc-cart-session.php(267): do_action('woocommerce_car…')

10 /var/www/html/wp-includes/class-wp-hook.php(308): WC_Cart_Session->set_session(Object(WC_Cart))

11 /var/www/html/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters('', Array)

12 /var/www/html/wp-includes/plugin.php(517): WP_Hook->do_action(Array)

13 /var/www/html/wp-content/plugins/woocommerce/includes/class-wc-cart-session.php(208): do_action('woocommerce_car…', Object(WC_Cart))

14 /var/www/html/wp-includes/class-wp-hook.php(308): WC_Cart_Session->get_cart_from_session('')

15 /var/www/html/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters(false, Array)

16 /var/www/html/wp-includes/plugin.php(517): WP_Hook->do_action(Array)

17 /var/www/html/wp-settings.php(639): do_action('wp_loaded')

18 /var/www/html/wp-config.php(101): require_once('/var/www/html/w…')

19 /var/www/html/wp-load.php(50): require_once('/var/www/html/w…')

20 /var/www/html/wp-blog-header.php(13): require_once('/var/www/html/w…')

21 /var/www/html/index.php(17): require('/var/www/html/w…')

22 {main}

Any idea?