Permit to add items to cart from other code with a plugin or component

[inode64]

I have made a component to add items to cart, but I have found a problem when I tried to add a item through the other plugin or component outside of virtuemart.
Virtuemart inserts items to cart by using a POST to get quantity

Currently using VM3.2.12 on Joomla 3.8.7 PHP 7.0.25

My example code to insert items in cart.
--------------

                $cart = VirtuemartCart::getCart();
                if (!$cart) {
                        JError::raiseWarning(500, 'Error');
                        return false;
                }

                $error = true;
                $cart->add($pks, $error);

And the patch permit to it

--- components/com_virtuemart/helpers/cart.php.old    2018-01-10 12:43:32.129002324 +0100
+++ components/com_virtuemart/helpers/cart.php    2018-02-22 18:45:29.785968463 +0100
@@ -512,11 +512,7 @@
                 $productData['virtuemart_product_id'] = (int)$virtuemart_product_id;
             }

-            if(!empty( $post['quantity'][$p_key])){
-                $productData['quantity'] = (int) $post['quantity'][$p_key];
-            } else {
-                    continue;
-            }
+            $productData['quantity'] = (empty( $post['quantity'][$p_key]) ? 1 : (int) $post['quantity'][$p_key]);

             if(!empty( $post['customProductData'][$virtuemart_product_id])){
                 //$productData['customProductData']