outof(): Mail NULL fix..
Even if i have rewritten outof() completely to be able to
support unlimited pipe targets and allow intermixing of pipes
and files (outof(): FIX and recode.., 2012-10-04), and
fixed/tweaked my rewrite twice, first (Tweak (outof(): FIX and
recode.., 2012-10-04).., 2012-10-09), followed by (outof():
better error verbosity, add missed senderr tracking, 2012-10-17)
is still have missed an important point.
The file expansion may fail, thus resulting in a NULL return,
which was not yet handled.
This error also exists in FreeBSD and NetBSD mailx(1).