當在 commerce js 中訪問購物車對象的 line_items 數組時，我收到一條錯誤，指出它未定義，但我仍然可以在控制臺中看到它。這是一些屏幕截圖：錯誤：TypeError: Cannot read property 'length' of undefinedCartD:/Zayeed/Projects/e_commerce/src/components/Cart/Cart.jsx:7   4 |    5 | const Cart = ({ cart }) => {   6 |     const classes = useStyles();>  7 |     const isEmpty = !cart.line_items.length;   8 |    9 |     const EmptyCart = () => (  10 |         <Typography variant="subtitle1">You have no items in your cart, start adding some.</Typography我的代碼：import React from 'react'import { Container, Typography, Button, Grid } from '@material-ui/core'import useStyles from './styles';const Cart = ({ cart }) => {    const classes = useStyles();    const isEmpty = !cart.line_items.length;    const EmptyCart = () => (        <Typography variant="subtitle1">You have no items in your cart, start adding some.</Typography>    );    const FilledCart = () => {        <>            <Grid container spacing={3}>                {cart.line_items.map(item => (                    <Grid item xs={12} sm={4} key={item.id}>                        <div>{item.name}</div>                    </Grid>                ))}            </Grid>            <div className={classes.cardDetails}>                    <Typography variant="h4">Subtotal: {cart.subtotal.formatted_with_symbol}</Typography>                    <div>                        <Button className={classes.emptyButton} size="large" type="button" variant="contained" color="secondary">Empty Cart</Button>                        <Button className={classes.checkout} size="large" type="button" variant="contained" color="primary">Checkout</Button>                    </div>            </div>        </>    }    return (        <Container>            <div className={classes.toolbar}/>            <Typography className={classes.title} variant="h3">Your Shopping Cart:</Typography>            {isEmpty ? <EmptyCart/> : <FilledCart />}        </Container>    )}export default Cart似乎道具沒有按預期導入，我無法訪問購物車對象的任何屬性。