fix 2 other minetest.item_drops

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, "", pos)
+					minetest.item_drop(stack, nil, pos)
 					stack:set_count(1)
 					stack:set_wear(0)
 					inv:set_stack("recipe", idx, stack)

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, "", pos)
+					minetest.item_drop(stack, nil, pos)
 				end
 			end
 		end