Material editor broken

The material editor doesn't respond to changing shaders via typing or File -> Import. I did some basic debugging and it seems that `materialadapter` is broken. I'll poke around for a while longer and see if I can find a fix.

Likely unrelated to this bug, but without a dark theme the yellow syntax highlighting is unreadable.

Edit: Dark mode and editor are working in 6.4 so this is a regression.