Fix PHP 8.1 Diffusion history errors

Summary:
Fix multiple PHP 8.1 errors when viewing Diffusion history.

Fixes T15573

Test Plan: View a diffusion history page. Eg https://my.php81.phorge.site/source/myrepo/history/master/

Reviewers: O1 Blessed Committers, speck

Reviewed By: O1 Blessed Committers, speck

Subscribers: speck, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15573

Differential Revision: https://we.phorge.it/D25366