Recognize that NULL is an invalid cap_t and cap_iab_t.

This was a regresssion introduced in libcap-2.55. Fixed in libcap-2.59.
Added a cap_launch NULL test too. Comparing against NULL would cause a
SIGSEGV against these library revisions.

Signed-off-by: Andrew G. Morgan <morgan@kernel.org>
5 files changed