类型错误 [ERR_INVALID_ARG_TYPE]：“数据”参数必须是字符串类型或 Buffer、TypedArray 或 DataView 的实例。收到未定义

Question

我正在尝试从待办事项列表应用程序中删除用户帐户，但不幸的是我收到错误消息。尝试从待办事项列表应用中删除用户时出现此错误

这是我的代码。

server.delete("/user/delete", async function(req, res){
  const newDeleteUser = new user(req.body.username, req.body.password);
  await newDeleteUser.delete();
  res.status(200).json(newDeleteUser).end();
  console.log(req.body);
});

class User {
    constructor(username, password) {
        this.username = username;
        this.password = crypto.createHmac('sha256', secret)
            .update(password)
            .digest('hex');
        this.valid = false;
    }

    async delete(){
        try{
            let response = await database.deleteUser(this.username,this.password);
            return response;
        }catch(error){
            console.error(error)
        }
    }
    

}

async deleteUser(username, password){
        const client = new pg.Client(this.credentials);
        let results = null;
        try{
            await client.connect();
            results = await client.query('DELETE FROM "public"."users" WHERE username = $1 and password = $2 RETURNING *;', [username, password]);
            client.end();
        }catch(err){
            client.end();
            console.log(err);
            results = err;
        }

        return results;
    }

请帮忙