Optional dependency on default mod (#182)

sounds.lua

@@ -0,0 +1,20 @@
+--[[
+More Blocks: sound definitions
+
+Copyright © 2011-2021 Hugo Locurcio and contributors.
+Licensed under the zlib license. See LICENSE.md for more information.
+--]]
+
+local has_default_mod = minetest.get_modpath("default")
+for _, sound in ipairs({"dirt", "wood", "stone", "metal", "glass", "leaves"}) do
+    -- use sound-function from default if available
+    -- otherwise fall back to a no-op function (no sounds)
+    local sound_function_name = "node_sound_" .. sound .. "_defaults"
+    if has_default_mod then
+        -- use default sounds
+        moreblocks[sound_function_name] = default[sound_function_name]
+    else
+        -- no-op
+        moreblocks[sound_function_name] = function() end
+    end
+end