Allow objects to be linked even if they are missing other fields

Summary: Fixes T5717. Like other partial edits, object links should not be blocked by unrelated missing fields on the object.

Test Plan:
  - Linked two objects.
  - Verified the inverse editor already sets "continue on missing fields" and "continue on no effect".

Reviewers: chad, btrahan, joshuaspence

Reviewed By: joshuaspence

Subscribers: epriestley

Maniphest Tasks: T5717

Differential Revision: https://secure.phabricator.com/D10059

src/applications/search/controller/PhabricatorSearchAttachController.php

@@ -106,7 +106,9 @@ final class PhabricatorSearchAttachController
 
           $txn_editor = $object->getApplicationTransactionEditor()
             ->setActor($user)
-            ->setContentSourceFromRequest($request);
+            ->setContentSourceFromRequest($request)
+            ->setContinueOnMissingFields(true);
+
           $txn_template = $object->getApplicationTransactionTemplate()
             ->setTransactionType(PhabricatorTransactions::TYPE_EDGE)
             ->setMetadataValue('edge:type', $edge_type)