Backgrounds in categories show up as static dominant values instead of the background image if all image properties are not defined in the json.
https://github.com/klikli-dev/modonomicon/blob/b623bdcdebf3fba8c0a5f17fb725b300b70b120b/fabric/src/generated/resources/data/modonomicon/modonomicon/books/demo/categories/formatting.json#L3C1-L6C27
Not including this snippet (even as default values) will cause backgrounds to show up incorrectly