Hi Henri,
What version of Quark are you using? Did you download the code from the Github respository in the last couple of days?
The above error was introduced in the last couple of days while updating the theme. It was introduced after I updated the Options Framework. The code on Github was updated but the theme here, in the Theme Directory, was never updated so the version of the theme that you can download here (v1.2.6) works fine.
If you did download the code from my Github repo, then please download the latest version again. I’ve just fixed up the issue and pushed it to Github this afternoon.
Also, in future, as per the Forum Welcome, could you please post your own topic. Thanks.