wp-e-commerce/WP-e-Commerce — pull request #1669 by jjeaton (2014-11-26 02:51:02+00:00)
Title: Fix previous value parameter for update_product_meta

and delete_product_meta where the parameter was always forced to an empty string.

delete_product_meta isn't used at all and update_product_meta is only used once, so this is super obscure and probably has never caused an issue. :)