Make the wool dependency optional

The mod needs the wool and default mods only for the crafting recipes.
By registering the recipes only if the required nodes exist,
the mod is installable even without minetest_game or a similar game.

init.lua

@@ -31,14 +31,16 @@ for s,l in pairs(colours) do
 		groups = {oddly_breakable_by_hand=3,snappy=2,choppy=2},
 		sounds = dog_sounds,
 	})
-	minetest.register_craft({
-		output = name.." 6",
-		recipe = {
-			{"", "", ""},
-			{input, input, input},
-			{input, input, input},
-		}
-	})
+	if minetest.registered_nodes[input] then
+		minetest.register_craft({
+			output = name.." 6",
+			recipe = {
+				{"", "", ""},
+				{input, input, input},
+				{input, input, input},
+			}
+		})
+	end
 end
 
 
@@ -116,10 +118,13 @@ for dog,data in pairs(dogs) do
 			end
 		end,
 	})
-	minetest.register_craft({
-		output = name.." 6",
-		recipe = recipe
-	})
+	if minetest.registered_nodes["wool:white"]
+	and minetest.registered_nodes["default:torch"] then
+		minetest.register_craft({
+			output = name.." 6",
+			recipe = recipe
+		})
+	end
 	minetest.register_abm({
 		nodenames = {name},
 		interval = 1.5,

mod.conf

@@ -1,4 +1,4 @@
 name = dogblocks
 title = DogBlocks
 description = Cute, adorable dog nodes
-depends = wool
+optional_depends = default,wool