[mcl_craftguide] fix warnings

mods/HELP/mcl_craftguide/init.lua

@@ -417,9 +417,9 @@ local function get_tooltip(item, groups, cooktime, burntime)
 			-- and just print the normal item name without special formatting
 			if groups[1] == "compass" or groups[1] == "clock" then
 				groupstr = reg_items[item].description
-			elseif group_names[groups[1]] then
+			elseif g then
 				-- Use the special group name string
-				groupstr = minetest.colorize(gcol, group_names[groups[1]])
+				groupstr = minetest.colorize(gcol, g)
 			else
 				--[[ Fallback: Generic group explanation: This always
 				works, but the internally used group name (which