Here is my useEffect with a simple clean-up function () => { inbox?.destroy(); }, but it raises a warning when I let the clean-up function there. Why is that, isn't the clean-up function a legit syntax? How to fix it (of course without removing the clean-up function)?

  useEffect(() => {

    const { currentUser } = initialState!;

    let inbox: Talk.Inbox;

    if (!currentUser || !talkjsContainerRef.current) return;



    Talk.ready.then(async () => {

      const me = employeeToUser(currentUser);

      window.talkSession = new Talk.Session({ appId, me });

      if (id === undefined) {

        // me without other => most recent message first

        inbox = window.talkSession.createInbox();

      } else {

        // me with an other => select other

        const other = employeeToUser(await readEmployee(Number(id)));

        const conversation = window.talkSession.getOrCreateConversation(Talk.oneOnOneId(me, other));

        conversation.setParticipant(me);

        conversation.setParticipant(other);

        inbox = window.talkSession.createInbox({ selected: conversation });

      }

      inbox.mount(talkjsContainerRef.current);

    });



    return () => {

      inbox?.destroy();

    };

  }, [id, initialState]);