Fix an issue with adding or updating images in unified diff view

Summary: Fixes T8069.

Test Plan: Viewed a new image in unified diff view.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T8069

Differential Revision: https://secure.phabricator.com/D13217

src/applications/differential/render/DifferentialChangesetOneUpRenderer.php

@@ -225,7 +225,7 @@ final class DifferentialChangesetOneUpRenderer
         'file' => $new_file,
         'line' => 1,
         'oline' => ($old_file ? 1 : null),
-        'render' => $this->renderImageStage($old_file),
+        'render' => $this->renderImageStage($new_file),
       );
     }