WC 2.3.5 add_to_cart allowed memory exhausted

We are using a custom function to add a product to cart:
function add_product_to_cart()
{
if (!is_admin())
{
global $woocommerce;
$product_id = $_POST[‘credit_id’];
$found = false;
//check if product already in cart
if ( sizeof( $woocommerce->cart->get_cart() ) > 0 )
{
foreach ( $woocommerce->cart->get_cart() as $cart_item_key => $values )
{
$_product = $values[‘data’];
if ( $values[“id”] == $product_id )
$found = true;
}
// if product not found, add it
if ( ! $found )
$woocommerce->cart->add_to_cart( $product_id );
} else {
// if no products in cart, add it
$woocommerce->cart->add_to_cart( $product_id );
}
}
header(“location:”.$woocommerce->cart->get_cart_url());
}

When the cart is empty, we are getting following error from the function in wc-cart “get_cart_from_session”:
Fatal error: Allowed memory size of 100663296 bytes exhausted (tried to allocate 130968 bytes) in /wp-content/plugins/woocommerce/includes/class-wc-cart.php on line 252