geom: fix glabel status not showing components
Also fix some typos and move a couple NULL checks earlier.
Reviewed by: mckusick, Johan Söllvander, markj, kevans, adrian
Fixes: 0d4642a67e59f8da5e00a05001c342bdad2a806f
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D53180