Uncaught TypeError: Cannot read properties of undefined (reading 'type') with the redux-toolkit i'm facing this bug - redux-toolkit

Question

I'm facing this error when I'm trying to a request my backend I'm using the redux toolkit for my project I read the documentation also but I can't understand why this is happening I'm a beginner in the redux toolkit so kindly assess me in this
here is my users like page
const signup = createAsyncThunk(
// you can there any thing its all your choice
'datauser/signup',
async (user, thunkAPI) => {
try {
const response = await userapi.signup(user)
console.log(response)
return response.data
} catch (error) {
const message =
(error.response &&
error.response.data &&
error.response.data.message) ||
error.message ||
error.toString()
return thunkAPI.rejectWithValue(message)
}
}
)
// initialize the state from there
const initialState = {
user: user?user:null,
isError: false,
isSuccess: false,
isLoading: false,
message: '',
}
export const registerslice = createSlice({
// name=.e.t.c is the type of the state
name: 'user',
initialState,
reducers: {
reset: (state) => {
state.isLoading = false
state.isSuccess = false
state.isError = false
state.message = ''
},
},
extraReducers: (builder) => {
builder
.addCase(signup.fulfilled, (state, action) => {
state.isLoading = false
state.isSuccess = true
state.user = action.payload
})
}
})
// Action creators are generated for each case reducer function
export const { reset } = registerslice.actions
export default registerslice.reducer
here is my apislice
const API = 'http://localhost:5000'
// register user
const signup= async(response,userData)=>{
const res=axios.post(`${API}/signup`,userData)
if (response.data) {
localStorage.setItem('user', JSON.stringify(response.data))
}
return res.data
}
this is my store
import userReducer from '../redux/userSlice'
export const store = configureStore({
reducer: {
auth: userReducer,
},
})