forms: Fix advanced search on fields with a `name`

Previously, advanced search was bugged in such a way that the advanced
search on a field without a `name` value would result in a hit of all the
tickets.

Fixes osTicket/osTicket-1.8#288
Merge pull request #290 from greezybacon/issue/288

forms: Fix advanced search on fields without a `name`

Reviewed-By: Peter Rotich <peter@osticket.com>