Error code 18 must contain at least one message: invalid request using CosmJS

[deployRama]

Hello everyone.
I'm trying to learn different ways to send transactions. I use CosmJS.
Using the singAndBroadcast function of the client created with SigningStargatClient everything flows very well.
The problem arises when I try to make a transaction using first the sign function and then broadcastTx. It returns error 18 and tells me that the transaction must have at least one message, it actually has a message, I would not be understanding why it gives me that error.

const { SigningStargateClient, coins } = require('@cosmjs/stargate');
const { Secp256k1HdWallet } = require('@cosmjs/launchpad');


const rpcEndpoint = 'https://rpc-t.cosmos.nodestake.top/'; //testnet theta-testnet-001

const amount = coins(1, 'uatom');

async function main() {

    console.log(amount)

    const mnemonic = 'Seed'; //develompent
    const signer = await Secp256k1HdWallet.fromMnemonic(mnemonic, { prefix: "cosmos" });


    const client = await SigningStargateClient.connectWithSigner(rpcEndpoint, signer);
    const account = (await signer.getAccounts())[0].address;
    console.log(account)


    const messages = [
        {
            typeUrl: '/cosmos.bank.v1beta1.MsgSend',
            value: {
                fromAddress: account,
                toAddress: account,
                amount: amount,
            },
        },
    ];




    const fee = {
        amount: [{ amount: '606', denom: 'uatom' }],
        gas: '790000',
    };
    const memo = 'Testing';


    const { accountNumber, sequence } = await client.getSequence(account);
    console.log(accountNumber, sequence)


    const signerData = {
        accountNumber: accountNumber,
        sequence: sequence,
        chainId: 'theta-testnet-001',

    };
    console.log(messages)

    const signedTx = await client.sign(account, messages, fee, memo, signerData);



    const result = await client.broadcastTx(signedTx);

    console.log(result)
}

main()