Fix PHP Product Class and Stats PHP errors
Errors were result of instantiating a product using a product id corresponding to a product that was deleted.  As this is a normal occurrence as products come and go from a store the instantiation isn't the problem, but doing some operations on it is a problem.

Before doing these operations a check is made to see if they are permitted.
update doc block @since
Update @param, as none are provided.
Removed extra white space on $this->post
Merge pull request #1386 from JeffPyeBrook/pr-1376-stats-class-product-errors-rebased

Fix PHP Product Class and Stats PHP errors