MFC r314189,r314190,r314191:

MFC r314189,r314190,r314191:

r314189:

Fix up NULL/'\0' uses and fix 2 derefs after NULL

CID:		1018898, 1018899

r314190:

Fix some minor style nits: put parentheses around return values

r314191:

Fix up r314189

The conditional in do_buff_decode(..) after the while loop was accidentally
inverted. Only increment the pointer for fmt if it's not NUL.

git-svn-id: svn://svn.freebsd.org/base/stable/10@315122 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f