innd(8), nnrpd(8) filter return value

[Kevin Shell]

Hello list.
Another question again. :-)

  The filter documentations say that
innd(8) nnrpd(8) accepts an article if filter_art and filter_post function
returns empty string, rejects an article if otherwise returns nonempty string.
If filter_art and filter_post written not to return any value(not even empty string),
how innd(8), nnrpd(8) behaves?
Accepts or rejects or skips decision and does somthing else?

--
kevin