Check for zero argc in ksu

Most programs in the tree will perform a null dereference when argc is
zero, but as a setuid program ksu should be extra careful about memory
errors, even if this one is harmless.  Check and exit with status 1
immediately.

https://github.com/krb5/krb5/commit/c5b0a998d6349f8c90821a347db5666aed0e50eb
Author: Greg Hudson <ghudson@mit.edu>
Commit: c5b0a998d6349f8c90821a347db5666aed0e50eb
Branch: master
 src/clients/ksu/main.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)