Addition of SBA product without attribute selected

[mc12345678]

As identified by soxophoneplayer in the zen-cart site: https://www.zen-cart.com/showthread.php?47180-Stock-by-Attribute-v4-0-addon-for-v1-3-5-1-3-9&p=1348275#post1348275

attempting to add a product that has attributes, is tracked by SBA, but without any attributes selected potentially causes an error log to be generated as seen in this list of "common" code:

        #1  products_with_attributes_class_stock->zen_get_sba_attribute_info() called at [root/includes/extra_cart_actions/stock_by_attributes.php:883]
        #2  include(root/includes/extra_cart_actions/stock_by_attributes.php) called at [root/includes/main_cart_actions.php:26]
        #3  require(root/includes/main_cart_actions.php) called at [root/includes/init_includes/init_cart_handler.php:44]
        #4  require(root/includes/init_includes/init_cart_handler.php) called at [root/includes/autoload_func.php:48]
        #5  require(root/includes/autoload_func.php) called at [root/includes/application_top.php:170]
        #6  require(root/includes/application_top.php) called at [root/index.php:26]