Woocommerce: Latest update 2.3.5 is creating issues with snippet (add item on user visit)

Today I updated to the latest Woocommerce version and my website suddenly stoppped working. After some inspection, I found the latest update is crashing with a snippet I’m currently using to add items automatically on user visit which I found here:

http://docs.woothemes.com/document/automatically-add-product-to-cart-on-visit/

add_action( 'template_redirect', 'add_product_to_cart' );
function add_product_to_cart() {
    if ( ! is_admin() ) {
        $product_id = 64;
        $found = false;
        //check if product already in cart
        if ( sizeof( WC()->cart->get_cart() ) > 0 ) {
            foreach ( WC()->cart->get_cart() as $cart_item_key => $values ) {
                $_product = $values['data'];
                if ( $_product->id == $product_id )
                    $found = true;
            }
            // if product not found, add it
            if ( ! $found )
                WC()->cart->add_to_cart( $product_id );
        } else {
            // if no products in cart, add it
            WC()->cart->add_to_cart( $product_id );
        }
    }
}

Is there any aternative snippet that could work insted of this one?