Fix p's weird corrupt theme data crashing theme engine

For whatever reasons fse's p's theme data didn't have color information for some theme shadow, which crashed the whole thing. Probably caused by some pre-1.0 theme editor idk.

https://shigusegubu.club/notice/A3V392Cl2T6W9FApyi

Probably worth mentioning that multiple users reported this. I suspect this is probably caused by old data; we went from a Dec 2019 develop commit to 2.2.2.

if this works, then it seems fine by me

merged

mentioned in commit eb2975b6