EthereumSignedTransaction init always throws rlpItemInvalid

[robinwit]

Hi,

I'm trying to read an existing signed transaction in RLP format with Web3.swift:

let rlpBytes = Array(rlpData.bytes[1...]) // drop prefix
let rlpItems = try! RLPDecoder().decode(rlpBytes)
let tx = try! EthereumSignedTransaction(rlp: rlpItems)

The init of EthereumSignedTransaction runs fine, all the fields are properly extracted, but then line 583 is hit, which simply just seems to throw an error, always?

Shouldn't this be an else? I can open a PR to fix it.
Is this intended behavior in some way or am I misinterpreting the API?