Remove superfluous empty string
Remove superfluous empty string

This string previously contained a <CRLF> sequence, when commands were
still writing directly to the socket.

ref https://github.com/sstur/nodeftpd/pull/2
ref 22c8d1754d84b4ed1242a43ef89945ee4d95eb4f

sstur/nodeftpd,impaler/nodeftpd,oleksiyk/nodeftpd,phillipgreenii/nodeftpd