Lost stream after grav update

Hi,

I’ve upgraded without thinking Grav, and my site just broke. More precisely, the stream under theme:// delivers undefined.

https://www.mysite.com/undefined/css/style.css

If i’m using another theme, the urls are good, it’s just in my theme, which is not a child.

I don’t have a clue about what can break the theme path in a theme just with static files and yaml. Could you help in seeing more clear ?

Thank you !