handle optional dependencies better

init.lua

@@ -107,8 +107,7 @@ minetest.register_node("yl_dice:dice", {
 
 local BASE_BLOCK
 
-if minetest.get_modpath("yl_nether") then
+if minetest.registered_items["yl_nether:ivory_block"] then
-    -- FIXME check if this item is actually registered
     BASE_BLOCK = "yl_nether:ivory_block"
 end
 
@@ -122,6 +121,9 @@ if BASE_BLOCK then
             { "",         "",          "" },
         }
     })
+end
+
+if minetest.registered_items["dye:red"] then
     local colors = {
         "red",
         "blue",

mod.conf

@@ -1,2 +1,3 @@
 name = yl_dice
 description = Simple 6-sided dice
+optional_depends = yl_nether, dye