Fix EditEngine preview/draft for first comment on a task you didn't create

Summary: Ref T9132. See T9908#147038.

Test Plan:
  - As user A, created a new task.
  - As user B, started typing a comment on it (with no prior activity).
  - Users A and B must be different.

Before patch: preview/draft don't work, trace in error log (see above).

After patch: preview/draft work.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T9132

Differential Revision: https://secure.phabricator.com/D14678

src/applications/draft/storage/PhabricatorVersionedDraft.php

@@ -58,7 +58,7 @@ final class PhabricatorVersionedDraft extends PhabricatorDraftDAO {
     return id(new PhabricatorVersionedDraft())
       ->setObjectPHID($object_phid)
       ->setAuthorPHID($viewer_phid)
-      ->setVersion($version)
+      ->setVersion((int)$version)
       ->save();
   }