Plopp icons are blank in the built documentation

The static image of Plopp widgets in the tutorials of the documentation shows blanks where the toolbar icons should be.
This is not great as the tutorial isn't showing what the user would see if they run the notebook.

Example of the issue:

<img width="816" height="598" alt="Image" src="https://github.com/user-attachments/assets/52914563-9656-48d5-9fe4-3f5173843f7f" />