在 Laravel 9 中报错：Indirect modification of overloaded property ReturnOrder::$order has no effect

{
    "status_code": 500,
    "code": 0,
    "message": "Indirect modification of overloaded property ReturnOrder::$order has no effect",
    "trace": {
        "line": 648,
        "file": "E:\\object\\ReturnOrderService.php",
        "class": "ErrorException"
    }
}

$item->order = $keyedOrders[$item->order_id] ?? null;
$item->order->returnOrders = $keyedOrderReturnOrders[$item->order_id] ?? new EloquentCollection();

$item->order = $keyedOrders[$item->order_id] ?? null;
if ($item->order) {
	$item->order->returnOrders = $keyedOrderReturnOrders[$item->order_id] ?? new EloquentCollection();
}