mesecons_doors: Don't modify doors that are already mesecon-enabled

mesecons_doors/init.lua

@@ -22,6 +22,11 @@ end
 local function meseconify_door(name)
 	if minetest.registered_items[name .. "_b_1"] then
 		-- old style double-node doors
+		if minetest.registered_items[name .. "_b_1"].mesecons then
+			minetest.log("info", "[mesecons_doors] Not touching door " .. name)
+			return
+		end
+
 		local function toggle_state1 (pos)
 			on_rightclick(pos, 1, name.."_t_1", name.."_b_2", name.."_t_2", {1,2,3,0})
 		end
@@ -47,6 +52,10 @@ local function meseconify_door(name)
 		})
 	elseif minetest.registered_items[name .. "_a"] then
 		-- new style mesh node based doors
+		if minetest.registered_items[name .. "_a"].mesecons then
+			minetest.log("info", "[mesecons_doors] Not touching door " .. name)
+			return
+		end
 		local override = {
 			mesecons = {effector = {
 				action_on = function(pos)