Как сделать, чтобы товар без цены можно добавить в корзину? - [VM1] Модификации и хаки

/*** Add-to-Cart Button ***/
      if (USE_AS_CATALOGUE != '1' && $product_price != ""  && !stristr( $product_price, $VM_LANG->_PHPSHOP_PRODUCT_CALL )) {
         $form_addtocart = "<form action=\"". $mm_action_url ."index.php\" method=\"post\" name=\"addtocart\" id=\"addtocart".$i."\">\n
                <label for=\"quantity_".$i."\">".$VM_LANG->_PHPSHOP_CART_QUANTITY.":</label>\n
                <input id=\"quantity_".$i."\" class=\"inputbox\" type=\"text\" size=\"3\" name=\"quantity\" value=\"1\" />
                <input type=\"submit\" style=\"text-align:left;background-position:bottom left;width:30px;height:35px;cursor:pointer;border:none;font-weight:bold;font-family:inherit;background: url('". IMAGEURL ."ps_image/".PSHOP_ADD_TO_CART_STYLE ."') no-repeat left center transparent;vertical-align: middle;overflow:hidden;\" value=\""."\" title=\"".$VM_LANG->_PHPSHOP_CART_ADD_TO."\" />
                <input type=\"hidden\" name=\"category_id\" value=\"". @intval($_REQUEST['category_id']) ."\" />\n
                <input type=\"hidden\" name=\"product_id\" value=\"". $db_browse->f("product_id") ."\" />\n
                <input type=\"hidden\" name=\"page\" value=\"shop.cart\" />\n
                <input type=\"hidden\" name=\"func\" value=\"cartadd\" />\n
                <input type=\"hidden\" name=\"Itemid\" value=\"$Itemid\" />\n
                <input type=\"hidden\" name=\"option\" value=\"com_virtuemart\" />\n
              </form>\n";
      }
      else
      $form_addtocart = "";

/*** Add-to-Cart Button ***/
      if (USE_AS_CATALOGUE != '1' && $product_price != "" ) {
         $form_addtocart = "<form action=\"". $mm_action_url ."index.php\" method=\"post\" name=\"addtocart\" id=\"addtocart".$i."\">\n
                <label for=\"quantity_".$i."\">".$VM_LANG->_PHPSHOP_CART_QUANTITY.":</label>\n
                <input id=\"quantity_".$i."\" class=\"inputbox\" type=\"text\" size=\"3\" name=\"quantity\" value=\"1\" />
                <input type=\"submit\" style=\"text-align:left;background-position:bottom left;width:30px;height:35px;cursor:pointer;border:none;font-weight:bold;font-family:inherit;background: url('". IMAGEURL ."ps_image/".PSHOP_ADD_TO_CART_STYLE ."') no-repeat left center transparent;vertical-align: middle;overflow:hidden;\" value=\""."\" title=\"".$VM_LANG->_PHPSHOP_CART_ADD_TO."\" />
                <input type=\"hidden\" name=\"category_id\" value=\"". @intval($_REQUEST['category_id']) ."\" />\n
                <input type=\"hidden\" name=\"product_id\" value=\"". $db_browse->f("product_id") ."\" />\n
                <input type=\"hidden\" name=\"page\" value=\"shop.cart\" />\n
                <input type=\"hidden\" name=\"func\" value=\"cartadd\" />\n
                <input type=\"hidden\" name=\"Itemid\" value=\"$Itemid\" />\n
                <input type=\"hidden\" name=\"option\" value=\"com_virtuemart\" />\n
              </form>\n";
      }
      else
      $form_addtocart = "";