Fix edits of Ponder comments which mention other objects

Summary: Fixes T9806. See some discussion there.

Test Plan:
  - Edited a comment with `T12` in it.
  - Before change: exception.
  - After change: no exception.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T9806

Differential Revision: https://secure.phabricator.com/D14539

src/applications/ponder/editor/PonderAnswerEditor.php

@@ -10,6 +10,7 @@ final class PonderAnswerEditor extends PonderEditor {
     $types = parent::getTransactionTypes();
 
     $types[] = PhabricatorTransactions::TYPE_COMMENT;
+    $types[] = PhabricatorTransactions::TYPE_EDGE;
 
     $types[] = PonderAnswerTransaction::TYPE_CONTENT;
     $types[] = PonderAnswerTransaction::TYPE_STATUS;