如何在$project、mongoose(^5.2.13)中传递空对象

我想在中传递$project中的空对象mongoose.aggregate. 但我犯了个错误

{
    "ok": 0,
    "errmsg": "Invalid $project specification: specification must have at least one field",
    "code": 40177,
    "codeName": "Location40177",
    "name": "MongoError"
}

我的问题是

Catalog.aggregate([
    {
        $match: {}
    },
    {
        $project: {

        }
    }
])