아바타 nickname

[useProfile.js]

import React, { useCallback } from "react";
import { Card, Avatar, Button } from "antd";
import Link from "next/link";
import { useDispatch, useSelector } from "react-redux";
import { logoutRequestAction } from "../reducers/user";

function UserProfile() {
  const dispatch = useDispatch();
  const { me, isLoggingOut, nickname } = useSelector((state) => state.user);

  const onLogOut = useCallback(() => {
    dispatch(logoutRequestAction());
  }, []);

  return (
    <>
      <Card
        actions={[
          <div key="twit">
            나의 작성 글<br />0
          </div>,
          <div key="followings">
            팔로잉
            <br />0
          </div>,
          <div key="follower">
            팔로워
            <br />0
          </div>,
        ]}
      >
        <Card.Meta
          avatar={<Avatar>{me.nickname[0]}</Avatar>}
          title={me.nickname}
        />
        <Link href="/login">
          <Button onClick={onLogOut} loading={isLoggingOut}>
            로그아웃
          </Button>
        </Link>
      </Card>
    </>
  );
}

export default UserProfile;

[reducers/user.js]

export const initialState = {
  isLoggingIn: false, // 로그인 시도중 => ture가 되면 로딩창을 띄운다.
  isLoggedIn: false,
  isLoggingOut: false, // 로그아웃 시도중 => ture가 되면 로딩창을 띄운다.
  me: null,
  signUpData: {},
  loginData: {},
};

export const loginRequestAction = (data) => {
  return {
    type: "LOG_IN_REQUEST",
    data,
  };
};

export const logoutRequestAction = () => {
  return {
    type: "LOG_OUT_REQUEST",
  };
};

const reducer = (state = initialState, action) => {
  switch (action.type) {
    case "LOG_IN_REQUEST":
      console.log("리듀서 로그인");
      return {
        ...state,
        isLoggingIn: true,
      };
    case "LOG_IN_SUCCESS":
      return {
        ...state,
        isLoggingIn: false,
        isLoggedIn: true,
        me: { ...action.data, nickname: "leehyunju" },
      };
    case "LOG_IN_FAILURE":
      return {
        ...state,
        isLoggingIn: false,
        isLoggedIn: false,
      };
    // --------------------------------------------
    case "LOG_OUT_REQUEST":
      return {
        ...state,
        isLoggingOut: true,
      };
    case "LOG_OUT_SUCCESS":
      return {
        ...state,
        isLoggingOut: false,
        isLoggedIn: false,
        me: null,
      };
    case "LOG_OUT_FAILURE":
      return {
        ...state,
        isLoggingOut: false,
      };
    default:
      return state;
  }
};

export default reducer;

TypeError: Cannot read property 'nickname' of null

안녕하세요 ! 제로초님 ! 아바타에서 닉네임 첫글자 따오는 부분이 계속 오류가 나서 직접 해결해 보려고 하였으나 도저히 안되서 질문드립니다. useSelector로 user 리듀서 끌고왔는데 nickname 부분만 데이터가 안불러와지는데 어떤게 문제일까요 .........😥

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