wrong condition check for zero length read in SSLNetVConnection::net_read_io

int
SSLNextProtocolAccept::mainEvent(int event, void *edata)
{
  SSLNetVConnection *netvc = ssl_netvc_cast(event, edata);

  Debug("ssl", "[SSLNextProtocolAccept:mainEvent] event %d netvc %p", event, netvc);

  switch (event) {
  case NET_EVENT_ACCEPT:
    ink_release_assert(netvc != NULL);

    netvc->setTransparentPassThrough(transparent_passthrough);

    // Register our protocol set with the VC and kick off a zero-length read to
    // force the SSLNetVConnection to complete the SSL handshake. Don't tell
    // the endpoint that there is an accept to handle until the read completes
    // and we know which protocol was negotiated.
    netvc->registerNextProtocolSet(&this->protoset);
    //**** BELOW CODE SET UP A ZERO LENGTH READ VIO ****
    netvc->do_io(VIO::READ, new SSLNextProtocolTrampoline(this, netvc->mutex), 0, this->buffer, 0);
    netvc->set_session_accept_pointer(this);
    return EVENT_CONT;
  default:
    netvc->do_io(VIO::CLOSE);
    return EVENT_DONE;
  }
}

// changed by YTS Team, yamsat
void
SSLNetVConnection::net_read_io(NetHandler *nh, EThread *lthread)
{
.
.
.
  MIOBufferAccessor &buf = s->vio.buffer;
  int64_t ntodo = s->vio.ntodo();
  ink_assert(buf.writer());
.
.
.
    } else if (ret == EVENT_DONE) {
      // If this was driven by a zero length read, signal complete when
      // the handshake is complete. Otherwise set up for continuing read
      // operations.
      if (ntodo <= 0) {