[Erro create transaction with multi singature]

[Mehrdadgame]

Describe the bug
when add more than one signature in transaction don't open Phanton and have error : ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.

#Code

       var blockHash = await Web3.Instance.Wallet.ActiveRpcClient.GetRecentBlockHashAsync();
        Debug.Log($"{blockHash.Result.Value.Blockhash}");

        Account mintAccount = Web3.Instance.Wallet.Account;
        Debug.Log($"MintAccount: {mintAccount}");
        Account ownerAccount = new Account("", "9nQUWBRcx....LHGugZ9ES7FV");
        Debug.Log($"OwnerAccount: {ownerAccount}");
        Account initialAccount = new Account("", "87L945pDtHL...i5GxdQEnfqT");
        Debug.Log($"InitialAccount: {initialAccount}");

        var txBuilder = new TransactionBuilder()
            .SetRecentBlockHash(blockHash.Result.Value.Blockhash)
            .SetFeePayer(mintAccount)
            .AddInstruction(MemoProgram.NewMemo(mintAccount.PublicKey, "Hello Mehrdad :)"))
            .Build(new List<Account>() {mintAccount, ownerAccount, initialAccount});

        var sign = await Web3.Instance.Wallet.SignTransaction(Transaction.Deserialize(txBuilder));

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
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Desktop (please complete the following information):

• OS:[android]
• Browser [e.g. chrome, safari]
• Version Solana [ 0.1]

[GabrielePicco]

@Mehrdadgame couple of issues, ownerAccount and initialAccount have empty private keys, that will fail when signing.

Build method won't work for the same reason, if using an external wallet you should use Web3.Wallet.SignAndSendTransaction that will trigger the wallet signature.

Should be something like:

var blockHash = await Web3.Wallet.ActiveRpcClient.GetRecentBlockHashAsync();
Debug.Log($"{blockHash.Result.Value.Blockhash}");

Account mintAccount = Web3.Wallet.Account;
Debug.Log($"MintAccount: {mintAccount}");
Account ownerAccount = new Account();
Debug.Log($"OwnerAccount: {ownerAccount}");
Account initialAccount = new Account();
Debug.Log($"InitialAccount: {initialAccount}");

var txBuilder = new TransactionBuilder()
    .SetRecentBlockHash(blockHash.Result.Value.Blockhash)
    .SetFeePayer(mintAccount)
    .AddInstruction(MemoProgram.NewMemo(mintAccount.PublicKey, "Hello Mehrdad :)"))
    .Serialize();
var tx = Transaction.Deserialize(txBuilder);
tx.Sign(ownerAccount);
tx.Sign(initialAccount);
var sign = await Web3.Wallet.SignAndSendTransaction(tx);