this can occur if tiny_skia decides it doesn't like the path (e.g. circle with negative radius)
i don't really care to render these since they're degenerate cases anyways
this fixes the case where
(def botsbuildbots (fn () (botsbuildbots))) (botsbuildbots)
would not run properly (return with a "set def index out of bounds" error)
also make exceptions store String instead of &'static str for better error reporting
closes#33
liquidex