something is wrong when i try to use redux-toolkit

userSlice.js:22 Uncaught (in promise) TypeError: Cannot create property ‘error’ on string ‘User created successfully!’ at signInFailure (userSlice.js:22:19) at @reduxjs_toolkit.js?v=69e8a274:1773:26

#reducers for make requests to api in mern app

import { createSlice } from "@reduxjs/toolkit";

const initialState = {
  currentUser: null,
  error: null,
  loading: false,
};

const userSlice = createSlice({
  name: "user",
  initialState,
  reducers: {
    signInStart: (state) => {
      state.loading = true;
    },
    signInSuccess: (state, action) => {
      state.currentUser = action.payload;
      state.loading = false;
      state.error = null;
    },
    signInFailure: (state, action) => {
      state.error = action.payload; // Handle both object and string payloads
      state.loading = false;
    },

});

export const {
  signInStart,
  signInSuccess,
  signInFailure,

  signOutUserStart,
} = userSlice.actions;

export default userSlice.reducer;

i try make the payload is string but it not solve the broblem !

signInFailure: (state, action) => {  

  state.error = typeof action.payload === 'string' ? action.payload : 'An error occurred';  
  state.loading = false;