reducer부분에서 TypeError: 에러가 납니다.

##index.js 부분입니다.

import {Provider} from 'react-redux';
//리덕스 쓰기 위한 세팅
import { createStore } from 'redux';
import { stat } from 'fs-extra';

let 초기값 = [
    { id:0, name:'멋진신발', quan: 2},
    { id:1, name:'나이키에어맥스90', quan: 1},
    { id:2, name:'에어부스트', quan: 4}
  ];

function reducer(state = 초기값, 액션) {
  if(액션.type === '수량증가') {
    let 복사된값 = [...state];
    복사된값[0].quan++;
    return 복사된값
  } else {
    return state
  }
}

let store = createStore(reducer);

## 요기는 Cart.js 부분입니다.

                    {
                        props.p_state.map((a, i) => {
                        return (
                            <tr key={i}>
                                <td>{a.id}</td>
                                <td>{a.name}</td>
                                <td>{props.p_state[i].quan}</td>
                                <td><button onClick={()=>{
                                    props.dispatch({ type: '수량증가' })

                                }}>+</button></td>
                            </tr>
                        )           
                        })
                    }