Reported by @kallewoof here: https://github.com/bitcoin/bitcoin/pull/13917#issuecomment-412459298

```
$ ./bitcoin-cli createpsbt "[]" "[{\"$(./bitcoin-cli getnewaddress)\":0.01}]"
cHNidP8BACoCAAAAAAFAQg8AAAAAABepFG6Rty1Vk+fUOR4v9E6R6YXDFkHwhwAAAAAAAA==
$ ./bitcoin-cli decodepsbt cHNidP8BACoCAAAAAAFAQg8AAAAAABepFG6Rty1Vk+fUOR4v9E6R6YXDFkHwhwAAAAAAAA==
error code: -22
error message:
TX decode failed CDataStream::read(): end of data: unspecified iostream_category error
```

tx = std::move(mtx);
                    
                    for (const CTxIn& txin : tx->vin) {
                        if (!txin.scriptSig.empty() || !txin.scriptWitness.IsNull()) {
                            throw std::ios_base::failure("Unsigned tx does not have empty scriptSigs and scriptWitnesses.");
                        }
                    }
                    break;
                }
                
                default: {
                    if (unknown.count(key) > 0) {
                        throw std::ios_base::failure("Duplicate Key, key for unknown value already provided");
                    }
                    
                    std::vector<unsigned char> val_bytes;
                    s >> val_bytes;
                    unknown.emplace(std::move(key), std::move(val_bytes));
                }
            }
        }
        
        if (!tx) {
            throw std::ios_base::failure("No unsigned transcation was provided");
        }
        
        unsigned int i = 0;
        while (!s.empty() && i < tx->vin.size()) {
            PSBTInput input;
            s >> input;