[patch] avoid invoking commands with empty argument

[Adam Byrtek / alpha <alpha student uci agh edu pl>]

mc passes an empty argument ("") to the EDITOR when creating new file
(with F14). It makes vim to list the current dircetory. The nvi
doesn't create temporary file, so write command won't work, however if
you call nvi without any argument it creates a temp file to save the
data in. The same problem occur with some other editors (jed to name
one) 

Patch submitted:
https://savannah.gnu.org/patch/index.php?func=detailpatch&patch_id=1092&group_id=3521

-- 

  _.|._ |_  _.    : Adam Byrtek, alpha@(irc.pl|debian.org)
 (_|||_)| |(_|    : gg 1802819, pgp 0xB25952C0
     |            : jid alpha.pl(at)jabber.org