Oak UserManager#getAuthorizable handles null and empty string differently than Jackrabbit

With Jackrabbit, the following API call

UserManager#getAuthorizable(String auth)

with either null or "" used to throw

throw new IllegalArgumentException("Invalid authorizable name '" + id + "'");

With Oak UserManager, the same input does not throw an IAE, but instead return a null value when providing "" and throws a NPE when providing null.

From my POV, it would be best to avoid throwing exceptions on those two cases. Indeed, returning a null value is simpler for the API user and would comply with the API.
If so, the implementation in case of null may be changed in order to swallow the null value and the difference between Jackrabbit and Oak may be documented.