ZwQueryInformationProcess failing - but not failing

I ran across a situation where even though ZwQueryInformationProcess fails,
it retuns a success code. What I mean by failing is that the returned
length of the buffer is equal to sizeof(UNICODE_STRING), which means it
returned nothing.
The actual problem, and why I am posting about this, is that the API will
set the ->Buffer field to NULL in this case!
FYI.

Kind regards, Dejan.