Don't send null data events on a Socket stream.

runtime/bin/socket_patch.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 patch class RawServerSocket  {
   /* patch */ static Future<RawServerSocket> bind([String address = "127.0.0.1",
                                                    int port = 0,
                                                    int backlog = 0]) {
     return _RawServerSocket.bind(address, port, backlog);
   }
@@ skipping 813 matching lines @@
 
   void _onPauseStateChange() {
     if (_raw != null) {
       _raw.readEventsEnabled = !_controller.isPaused;
     }
   }
 
   void _onData(event) {
     switch (event) {
       case RawSocketEvent.READ:
-        _controller.add(_raw.read());
+        var buffer = _raw.read();
+        if (buffer != null) _controller.add(buffer);
         break;
       case RawSocketEvent.WRITE:
         _consumer.write();
         break;
       case RawSocketEvent.READ_CLOSED:
         _controllerClosed = true;
         _controller.close();
         break;
     }
   }
@@ skipping 68 matching lines @@
     _raw.onBadCertificate = callback;
   }
 
   X509Certificate get peerCertificate {
     if (_raw == null) {
      throw new StateError("peerCertificate called on destroyed SecureSocket");
     }
     return _raw.peerCertificate;
   }
 }