It doesn't work as I get the same error. The bow is a duplicate of the Bow of Elvenkind with the this bit taken out. Everything else is the same except the description text.
Code:
~ If we're not a elf, get out now
if (hero.tagis[Race.Elf] = 0) then
done
endif
Yeah I know I can just use adjustment to modify the bow. I made the material for Hero Lab for the rest of the group but I couldn't get my bow to work as it is a named item so you can't just change the material.