Cookbook "Create pages from frontend" Example kit generates error message

[gbdesign2023]

https://getkirby.com/docs/cookbook/forms/creating-pages-from-frontend

For a working example, download the demo "Eventkit".

Unfortunately, this is not 100 % true, as an error message appears immediately when the panel is called up. The sample data is from May 2019 and therefore already 5 years old. Is an adaptation to Kirby 4.3 necessary?