HPCC-19784 introduced methods to ISecUser and ISecResource in order to access embedded property iterators from concrete implementations. The implementations of these methods do not conform to conventional iterator usage.
CLdapSecUser always returns NULL, because it doesn't manage properties. Other implementations can return NULL, because embedded properties are lazily allocated and iterators are dependent upon the properties they iterate.
Conventional usage assumes returned iterators will not be NULL. All implementations need to be changed to not return NULL.