R1:27ea775fda5f

Fix a log warning when searching for ranges on custom "Date" fields

Summary:
See <https://discourse.phabricator-community.org/t/traceback-rendering-task-query-in-dashboard/2450/>.

It looks like this blames to D19126, which added some more complex constraint logic but overlooked "range" constraints, which are handled separately.

Test Plan:
- Added a custom "date" field to Maniphest with `"search": true`.
- Executed a range query against the field.

Then:

- Before: Warnings about undefined indexes…