MB-100 Don't crash if Min of Max is not an integer.

The can also be an atom infinity.

Change-Id: I734c6fa6bf1c646651211bb85214a98ae9130162
Reviewed-on: http://review.couchbase.org/28551
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>