update pipeworks

pipeworks/autocrafter.lua

@@ -223,7 +223,7 @@ local function upgrade_autocrafter(pos, meta)
 			if not recipe then return end
 			for idx, stack in ipairs(recipe) do
 				if not stack:is_empty() then
-					minetest.item_drop(stack, nil, pos)
+					minetest.add_item(pos, stack)
 					stack:set_count(1)
 					stack:set_wear(0)
 					inv:set_stack("recipe", idx, stack)

pipeworks/item_transport.lua

@@ -249,7 +249,10 @@ luaentity.register_entity("pipeworks:tubed_item", {
 			if not found_next then
 				drop_pos = minetest.find_node_near(vector.add(self.start_pos, velocity), 1, "air")
 				if drop_pos then
-					minetest.item_drop(stack, nil, drop_pos)
+					-- Using add_item instead of item_drop since this makes pipeworks backward
+					-- compatible with Minetest 0.4.13.
+					-- Using item_drop here makes Minetest 0.4.13 crash.
+					minetest.add_item(drop_pos, stack)
 					self:remove()
 					return
 				end

pipeworks/sorting_tubes.lua

@@ -6,7 +6,7 @@ if pipeworks.enable_mese_tube then
 			local inv = meta:get_inventory()
 			for i = 1, 6 do
 				for _, stack in ipairs(inv:get_list("line"..i)) do
-					minetest.item_drop(stack, nil, pos)
+					minetest.add_item(pos, stack)
 				end
 			end
 		end