prevent crash in setting sky color

if get color from name return nil

init.lua

@@ -128,7 +128,7 @@ unifieddyes.GREYS = {
 unifieddyes.GREYS_EXTENDED = table.copy(unifieddyes.GREYS)
 
 for i = 1, 14 do
-	if i ~= 0 and i ~= 3 and i ~= 7 and i ~= 11 and i ~= 15 then
+	if i ~= 0 and i ~= 4 and i ~= 8 and i ~= 11 and i ~= 15 then
 		table.insert(unifieddyes.GREYS_EXTENDED, "grey_"..i)
 	end
 end
@@ -449,7 +449,7 @@ function unifieddyes.getpaletteidx(color, palette_type)
 		["grey_14"] = 1,
 		["grey_13"] = 2,
 		["grey_12"] = 3,
-		["light_grey"] = 3,
+		["light_grey"] = 4,
 		["grey_11"] = 4,
 		["grey_10"] = 5,
 		["grey_9"] = 6,
@@ -668,10 +668,12 @@ function unifieddyes.on_airbrush(itemstack, player, pointed_thing)
 			minetest.chat_send_player(player_name, "*** No node selected")
 		else
 			local hexcolor = unifieddyes.get_color_from_dye_name(painting_with)
-			local r = tonumber(string.sub(hexcolor,1,2),16)
-			local g = tonumber(string.sub(hexcolor,3,4),16)
-			local b = tonumber(string.sub(hexcolor,5,6),16)
-			player:set_sky({r=r,g=g,b=b,a=255},"plain")
+			if hexcolor then
+				local r = tonumber(string.sub(hexcolor,1,2),16)
+				local g = tonumber(string.sub(hexcolor,3,4),16)
+				local b = tonumber(string.sub(hexcolor,5,6),16)
+				player:set_sky({r=r,g=g,b=b,a=255},"plain")
+			end
 		end
 		return
 	end
@@ -1431,7 +1433,7 @@ for _,i in ipairs(unifieddyes.base_color_crafts) do
 
 			minetest.register_craft( {
 				type = "shapeless",
-				output = "dye:"..j[1]..color..j[2].." "..yield,
+				output = "dye:"..j[1]..color..j[2].." "..j[6],
 				recipe = {
 					"dye:"..color,
 					firstdye,