Hey kdog, thanks for the report! This looks like the theme switching issue here: System theme changes can trigger RunTimeError · Issue #251 · glutanimate/image-occlusion-enhanced · GitHub
Basically, when the macOS theme switches between day/night mode, this can cause the add-on to produce this error message. The next update for Image Occlusion Enhanced will fix the underlying problem. Until then, feel free to just click the error message away, it won’t affect your Anki in any way.
Hope that helps for now!