Summary:
Fixes T12082. Ref T11114. When modular transaction render a handle list, they use HandleListView, which has a text mode.
However, the HandleListView is a TagView, and currently TagViews always render a tag of some kind. Allow them to return `null` to decline to render any tag.
Test Plan:
- Added a pile of debugging stuff to `ApplicationTransactionEditor` to throw during mail generation.
- Added a reviewer to a revision.
- Used `bin/worker execute --id ...` to hit the mail generation repeatedly.
- Before patch: mail generated with a <span>, even in text mode.
- After patch: clean mail generation.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T12082, T11114
Differential Revision: https://secure.phabricator.com/D17162
b08c9b3ffa