Exclude nulls in translator when operator is range, gt, gte

Previously, nulls were included in all cases making it appear that null
was but 0 and infinity. Now, null is effectively treated as 0.

Signed-off-by: Don Naegely <naegelyd@gmail.com>
Merge pull request #284 from cbmi/issue-282

Exclude nulls in translator when operator is range, gt, gte