Hi! Thank you for the report and I apologize for my delay in the answer.
This error refers to the splash0 image (it's the first image the game load) I'll check if there is something missing with the Mac version but I'm pretty sure it was all ok.
I'll update you soon!
EDIT: on the old version the image: "splash0" was buggy. on the 1.2.1 version I think it's working.
If someone with Mac can confirm...?