"abi: attempting to unmarshall an empty string while arguments are expected" from testnet

[mmsqe]

since smart contract function is the same but not sure why behaviour change when call balanceOf from mainnet and kovan

func test(network string, tokenAddr string) {
    userAddr := "0x43438cd9a239a10495bedd32c6e22048deb2e869"
    eth, err := getETH(fmt.Sprintf("https://%s.infura.io/v3/17ed7fe26d014e5b9be7dfff5368c69d", network))
    vcs := multicall.ViewCalls{
        multicall.NewViewCall(
            network,
            tokenAddr,
            "balanceOf(address)(uint256)",
            []interface{}{userAddr},
        ),
    }
    mc, _ := multicall.New(eth)
    block := "latest"
    res, err := mc.Call(vcs, block)
    if err != nil {
        panic(err)
    }
    result, _ := res.Calls[network]
    balance := result.Decoded[0].(*multicall.BigIntJSONString)
    balanceInt := big.Int(*balance)
    fmt.Println(network, balanceInt.String())
}

func main() {
    test("mainnet", "0xFFC97d72E13E01096502Cb8Eb52dEe56f74DAD7B")
    test("kovan", "0x76c6D190639a946E894D4A480806EB1D18391E01")
    // mainnet 0
    // panic: abi: attempting to unmarshall an empty string while arguments are expected
}