Make the reception of a null packet via TCP non-fatal.
Make the reception of a null packet via TCP non-fatal.

A null packet should not make ippusbxd terminate, as this would enable
normal users to kill the daemon, or simple administrator actions like
port scans with nmap kill the daemon. Now we simply ignore such a
packet and go on.

daniel-dressler/ippusbxd,tillkamppeter/ippusbxd