error when call return value is empty array int256[]

[ethers]

develop 16861fc

Make this call to specified contract:

I0519 17:27:16.918552   20188 api.go:37] eth_call [{"to":"0x96cd8aa2d6669fb548449df5ce7e90914d68753f","data":"0x734388060000000000000000000000000000000000000000000000000000000000000002"},"latest"]

Here's the response:

I0519 17:27:16.920878   20188 http.go:130] Generated response: *rpc.RpcSuccessResponse &{%!s(float64=12) 2.0 0x00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000}
I0519 17:27:16.920986   20188 http.go:141] Sending payload: {
    "id": 12,
    "jsonrpc": "2.0",
    "result": "0x00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000"
}

web3.js has error (param.dynamicPart() is "")
The error is BigNumber Error: new BigNumber() not a base 16 number (as in #211)

            SolidityType.prototype.formatOutput = function(param, arrayType) {
                if (arrayType) {
                    // let's assume, that we solidity will never return long arrays :P 
                    var result = [];
                    var length = new BigNumber(param.dynamicPart().slice(0, 64), 16);  <--- error

Here is the abi snippet if it helps; the return is array int256[] but with 0 elements:

{
    "name": "lookupTicket(int256)",
    "type": "function",
    "inputs": [{ "name": "ticketId", "type": "int256" }],
    "outputs": [{ "name": "out", "type": "int256[]" }]
}