Connector: check len(values) to avoid nil pointer dereference

[yunginnanet]

Do a len() check on values otherwise we could panic out here:

	status.Status = Status(values[1])
	status.Serial = values[3]
	status.Version = values[5]
	status.Pid = values[7]
	status.Address = values[9]
	status.Port = values[11]

https://github.com/yunginnanet/yubihsm-go/blob/995af3b2fdb55ee1eb1d21e54f5278cac19b2fa8/connector/http.go#L78-L83

This package not only needs test cases but probably some fuzzing as well. I'll do what I can.