fix fire arrows don't touch fire

mods/throwing/fire_arrow.lua

@@ -64,7 +64,7 @@ THROWING_ARROW_ENTITY.on_step = function(self, dtime)
 				end
 			end
 
-			if node.name ~= "air" and node.name ~= "throwing:light" then
+			if node.name ~= "air" and node.name ~= "throwing:light" and node.name ~= "fire:basic_flame" then
 				if node.name ~= "ignore" then
 					minetest.set_node(self.lastpos, {name="fire:basic_flame"})
 				end