Alt-tab (tabwin) Previews Not Working

I've noticed that tabwin previews are no longer working. Compositor option to show window previews is enabled. I'm running the latest git build of xfwm4. A git bisect has returned the following as a culprit:

a7971823de40a17dcba940fcef56d781626826d3 is the first bad commit
commit a7971823de40a17dcba940fcef56d781626826d3
Author: Olivier Fourdan <fourdan@xfce.org>
Date:   Mon Nov 1 16:04:19 2021 +0100

    icons: Gracefully handle non-existent icons

Let me know if you need any more info.