Ethers.js "Error: unknown account #0 (operation="getAddress", code=UNSUPPORTED_OPERATION)"

I'm trying to fetch the price of ETH from KyberSwap, using Ethers.js, but I'm receiving the following error:

Error: unknown account #0 (operation="getAddress", code=UNSUPPORTED_OPERATION, version=providers/5.5.3)

I'm connected to an Infura web socket to fetch the data. Here's my script:

const { ethers } = require("hardhat");
const kyberABI = require('./kyberABI.json')

const provider = new ethers.providers.WebSocketProvider(
    "wss://mainnet.infura.io/ws/v3/<project_id>")

const kyberNetworkProxyAddress = "0x818E6FECD516Ecc3849DAf6845e3EC868087B755"
const daiAddress = "0x6b175474e89094c44da98b954eedeac495271d0f"

const kyber = new ethers.Contract(
    kyberNetworkProxyAddress,
    kyberABI.kyberNetworkProxy,
    provider.getSigner(),
);

async function main() {
    // Update eth price from Kyber to reflect current market value
    let curEthPriceUSD
    const updateEthPrice = async () => {
        const results = await kyber.getExpectedRate(
            '0xeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee',
            daiAddress,
            1
        )
        curEthPriceUSD = results.expectedRate
    }
    await updateEthPrice()
    console.log('Current Ethereum price in USD is: ',
        ethers.utils.formatEther(curEthPriceUSD))
}

main()

How do I fix this error?

Found a fix for this in a related issue on Github.

Instead of using provider.getSigner() to initialize the kyber contract, I used a Wallet object and grabbed the signer from there:

const wallet = new ethers.Wallet(ethPrivkey, provider);
const signer = wallet.provider.getSigner(wallet.address);

const kyber = new ethers.Contract(
    kyberNetworkProxyAddress,
    kyberABI.kyberNetworkProxy,
    signer
);