Conduit: Improve error handling calling phid.lookup without names
Summary:
Avoid an ugly TypeError exception. Throw a proper error code instead.
```
EXCEPTION: (TypeError) PhabricatorObjectQuery::withNames(): Argument #1 ($names) must be of type array, null given, called in /var/www/html/phorge/phorge/src/applications/phid/conduit/PHIDLookupConduitAPIMethod.php on line 28 at [<phorge>/src/applications/phid/query/PhabricatorObjectQuery.php:17]
```
Closes T16440
Test Plan: Go to http://phorge.localhost/conduit/method/phid.lookup/ and press "Call Method"
Reviewers: O1 Blessed Committers, mainframe98
Reviewed By: O1 Blessed Committers, mainframe98
Subscribers: mainframe98, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Maniphest Tasks: T16440
Differential Revision: https://we.phorge.it/D26643