Don't send null data segments

lib/net.js

@@ -244,6 +244,7 @@ Object.defineProperty(Stream.prototype, 'readyState', {
 
 
 Stream.prototype._appendBucket = function (data, encoding, fd) {
+  // TODO reject empty data.
   var newBucket =  { data: data };
   if (encoding) newBucket.encoding = encoding;
   if (fd) newBucket.fd = fd;

src/node_io_watcher.cc

@@ -335,6 +335,8 @@ void IOWatcher::Dump(EV_P_ ev_prepare *w, int revents) {
 
       size_t l = Buffer::Length(buf_object);
 
+      if (l == 0) continue;
+
       assert(first_offset < l);
       iov[iovcnt].iov_base = Buffer::Data(buf_object) + first_offset;
       iov[iovcnt].iov_len = l - first_offset;