Fix checked mode failure

runtime/bin/socket_impl.dart

 // Copyright (c) 2011, 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.
 
 
 class _SocketBase {
   // Bit flags used when communicating between the eventhandler and
   // dart code. The EVENT flags are used to indicate events of
   // interest when sending a message from dart code to the
   // eventhandler. When receiving a message from the eventhandler the
@@ skipping 372 matching lines @@
     _closeHandler = callback;
   }
 
   bool _isListenSocket() => false;
 
   bool _isPipe() => _pipe;
 
   InputStream get inputStream() {
     if (_inputStream === null) {
       if (_handlerMap[_IN_EVENT] !== null ||
-          _handlerMap[_CLOSE_EVENT]) {
+          _handlerMap[_CLOSE_EVENT] !== null) {
         throw new StreamException(
             "Cannot get input stream when socket handlers are used");
       }
       _inputStream = new SocketInputStream(this);
     }
     return _inputStream;
   }
 
   OutputStream get outputStream() {
     if (_outputStream === null) {
@@ skipping 51 matching lines @@
   bool _seenFirstOutEvent = false;
   bool _closedRead = false;
   bool _closedWrite = false;
   bool _pipe = false;
   Function _clientConnectHandler;
   Function _clientWriteHandler;
   SocketInputStream _inputStream;
   SocketOutputStream _outputStream;
 }