Server panics if you give the wallet a type of zcashd and a bogus binary path

[rmisio]

Observed:

  "Wallet": {
    "Binary": "/the/wheels/on/the/bus/go/round/and/round",
    "FeeAPI": "https://btc.fees.openbazaar.org",
    "HighFeeDefault": 160,
    "LowFeeDefault": 20,
    "MaxFee": 2000,
    "MediumFeeDefault": 60,
    "RPCPassword": "",
    "RPCUser": "",
    "TrustedPeer": "",
    "Type": "zcashd"
  }

results in:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x4aa8e46]

goroutine 433 [running]:
github.com/OpenBazaar/openbazaar-go/vendor/github.com/btcsuite/btcd/rpcclient.(*Client).NextID(...)
	/Users/rob/develop/openbazaar/v2/go/src/github.com/OpenBazaar/openbazaar-go/vendor/github.com/btcsuite/btcd/rpcclient/infrastructure.go:168
github.com/OpenBazaar/openbazaar-go/vendor/github.com/btcsuite/btcd/rpcclient.(*Client).RawRequestAsync(0x0, 0x4fc1d7a, 0xd, 0x5b47710, 0x0, 0x0, 0x1)
	/Users/rob/develop/openbazaar/v2/go/src/github.com/OpenBazaar/openbazaar-go/vendor/github.com/btcsuite/btcd/rpcclient/rawrequest.go:45 +0x86
github.com/OpenBazaar/openbazaar-go/vendor/github.com/btcsuite/btcd/rpcclient.FutureRawResult.Receive(...)
	/Users/rob/develop/openbazaar/v2/go/src/github.com/OpenBazaar/openbazaar-go/vendor/github.com/btcsuite/btcd/rpcclient/rawrequest.go:77
github.com/OpenBazaar/openbazaar-go/vendor/github.com/btcsuite/btcd/rpcclient.(*Client).RawRequest(0x0, 0x4fc1d7a, 0xd, 0x5b47710, 0x0, 0x0, 0x5b1eb60, 0xc420103e58, 0x410d733, 0xc42028a050, ...)
	/Users/rob/develop/openbazaar/v2/go/src/github.com/OpenBazaar/openbazaar-go/vendor/github.com/btcsuite/btcd/rpcclient/rawrequest.go:77 +0x61
github.com/OpenBazaar/openbazaar-go/bitcoin/zcashd.(*ZcashdWallet).Balance(0xc421092cf0, 0x0, 0x0)
	/Users/rob/develop/openbazaar/v2/go/src/github.com/OpenBazaar/openbazaar-go/bitcoin/zcashd/wallet.go:213 +0x85
github.com/OpenBazaar/openbazaar-go/vendor/github.com/OpenBazaar/openbazaar-go/bitcoin.(*StatusUpdater).Start(0xc420149710)
	/Users/rob/develop/openbazaar/v2/go/src/github.com/OpenBazaar/openbazaar-go/vendor/github.com/OpenBazaar/openbazaar-go/bitcoin/status.go:35 +0x171
created by github.com/OpenBazaar/openbazaar-go/cmd.(*Start).Execute.func4
	/Users/rob/develop/openbazaar/v2/go/src/github.com/OpenBazaar/openbazaar-go/cmd/start.go:825 +0x83b
exit status 2

Expected:

No panic and it would be nice if the server could give some logging outlining that the wallet was unable to start with the reason.

[cpacia]

This may have been using old commits. Don't think it does this normally. When I enter an invalid path it just shuts off with log fatal.