Don't call minetest.add_item for empty itemstring

mods/ITEMS/mcl_core/functions.lua

@@ -90,6 +90,9 @@ end
 
 local function drop_attached_node(p)
 	local nn = minetest.get_node(p).name
+	if nn == "air" or nn == "ignore" then
+		return
+	end
 	minetest.remove_node(p)
 	for _, item in pairs(minetest.get_node_drops(nn, "")) do
 		local pos = {
@@ -97,9 +100,11 @@ local function drop_attached_node(p)
 			y = p.y + math.random()/2 - 0.25,
 			z = p.z + math.random()/2 - 0.25,
 		}
+		if item ~= "" then
 			minetest.add_item(pos, item)
 		end
 	end
+end
 
 -- Helper function for node actions for liquid flow
 local liquid_flow_action = function(pos, group, action)