Fix assign-on-close behavior for comment controller

Summary: Ref T2217. Missed this while converting this endpoint.

Test Plan: Closed an unassigned task, got assigned.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2217

Differential Revision: https://secure.phabricator.com/D7089

src/applications/maniphest/controller/ManiphestTransactionSaveController.php

@@ -165,7 +165,7 @@ final class ManiphestTransactionSaveController extends ManiphestController {
             ManiphestTaskStatus::STATUS_OPEN) {
           // Closing an unassigned task. Assign the user as the owner of
           // this task.
-          $assign = new ManiphestTransaction();
+          $assign = new ManiphestTransactionPro();
           $assign->setTransactionType(ManiphestTransactionType::TYPE_OWNER);
           $assign->setNewValue($user->getPHID());
           $transactions[] = $assign;