K 10
svn:author
V 5
ariff
K 8
svn:date
V 27
2006-04-04T17:32:48.000000Z
K 7
svn:log
V 333
MFC (revision 1.37)
A pointer was checked for NULL after dereferencing it. The check is
not needed here, except there's a bug which results in detaching the
device twice.

Move the NULL pointer check to the beginning of the function and
convert it into a KASSERT.

CID:		483
Found with:	Coverity Prevent(tm)
Approved by:	re (scottl)

END