TypeError: Cannot read properties of undefined (reading 'address')

[Merrick17]

Hello i used the the secret key to recover the keyPair and generate a wallet , when triying i get this error ,
TypeError: Cannot read properties of undefined (reading 'address')
this is my Wallet Class :
`import { Buffer } from "buffer";
import { Keypair, PublicKey, Transaction } from "@solana/web3.js";

export default class Wallet {
private payer: Keypair;
constructor(payer: Keypair) {
this.payer = payer;
}

async signTransaction(tx: Transaction): Promise {
tx.partialSign(this.payer);
return tx;
}

async signAllTransactions(txs: Transaction[]): Promise<Transaction[]> {
return txs.map((t) => {
t.partialSign(this.payer);
return t;
});
}

get publicKey(): PublicKey {
return this.payer.publicKey;
}
}
`

and this is the implementation of my client
`import { Provider, BN } from "@project-serum/anchor";
import { Connection, PublicKey, Transaction, Keypair } from "@solana/web3.js";
import { TokenListProvider } from "@solana/spl-token-registry";
import { Swap } from "@project-serum/swap";

const DECIMALS = 6;
import Wallet from "../types/Wallet";

async function swapClient(wallet: Wallet) {
const provider = new Provider(
new Connection("https://api.mainnet-beta.solana.com", "recent"),
wallet,
Provider.defaultOptions()
);
const tokenList = await new TokenListProvider().resolve();
return new Swap(provider, tokenList);
}`