Table view header icons are not shown in macOS 26

This is how it looked in my VM, running Vienna 3.10.0 beta 5:
<img width="1315" height="886" alt="Image" src="https://github.com/user-attachments/assets/70be690b-a825-480b-8073-90244817822a" />

I didn't notice any log entries that explain why these images are not shown. 