Conduit: Improve error handling calling phid.query without PHIDs
Summary:
Avoid an ugly TypeError exception. Throw a proper error code instead.
```
EXCEPTION: (TypeError) PhabricatorHandleQuery::withPHIDs(): Argument #1 ($phids) must be of type array, null given, called in /var/www/html/phorge/phorge/src/applications/phid/conduit/PHIDQueryConduitAPIMethod.php on line 28 at [<phorge>/src/applications/phid/query/PhabricatorHandleQuery.php:12]
```
Closes T16439
Test Plan: Go to http://phorge.localhost/conduit/method/phid.query/ and press "Call Method"
Reviewers: O1 Blessed Committers, mainframe98
Reviewed By: O1 Blessed Committers, mainframe98
Subscribers: mainframe98, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Maniphest Tasks: T16439
Differential Revision: https://we.phorge.it/D26642