MB-10476: assert() may be empty macro

Change-Id: Ib02deb3367d467db416edc0b364116c619122b72
Reviewed-on: http://review.couchbase.org/34550
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>