Fix PHP 8.1 "strlen(null)" exception on auth email message body when PhabricatorAuthMessage is unset
Summary:
This is a fix for running Phorge on PHP 8.2+. Other fixes were already merged.
Closes T15536
Test Plan: Unclear.
Reviewers: O1 Blessed Committers, avivey, aklapper
Reviewed By: O1 Blessed Committers, avivey, aklapper
Subscribers: aklapper, avivey, speck, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Tags: #php_8_support
Maniphest Tasks: T15064, T15536
Differential Revision: https://we.phorge.it/D25256