The lua script "Gradius-BulletHell.lua" throws an exception due to an undefined function "get_vdir". The fix is to change all "get_vdir(s,vic)" to "getvdir(s.x,s.y, vic.x,vic.y)". I couldn't find an already-updated version of the script anywhere. Last known version on wayback machine has the issue too. https://web.archive.org/web/20090619063228/http://morphcat.de:80/lua/Gradius-BulletHell.lua
Note: Script is for PAL version of Gradius.
fixed at https://github.com/TASVideos/fceux/commit/b8c484ed1f03ebc6b8bad11dcf9a7f9e918168e5