Probably fix notifications not being properly marked as unread

Summary: Fixes T8586. This wasn't quite right in D13320.

Test Plan: iiam

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T8586

Differential Revision: https://secure.phabricator.com/D13331

src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php

@@ -1058,7 +1058,7 @@ abstract class PhabricatorApplicationTransactionEditor
       $mailed = array();
       foreach ($messages as $mail) {
         foreach ($mail->buildRecipientList() as $phid) {
-          $mailed[$phid] = true;
+          $mailed[$phid] = $phid;
         }
       }