tep_not_null update using get_object_vars

When $value is an object then we have to check if it has object vars because according to PHP manual "Objects with no properties are no longer considered empty."  http://us1.php.net/manual/en/function.empty.php

So is_null($value) when $value is an object it always return false. So the appropriate way to check is using get_object_vars which will return newProp, but the protected and private members will not be returned.
Merge pull request #180 from gadlol/patch-5

tep_not_null update using get_object_vars