Error handling and code cleanup

pkg/analysis_server/lib/src/protocol.dart

 // Copyright (c) 2014, 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.
 
 library protocol;
 
 import 'dart:convert' show JsonDecoder;
 
 /**
  * Instances of the class [Request] represent a request that was received.
@@ skipping 59 matching lines @@
   factory Request.fromString(String data) {
     try {
       var result = DECODER.convert(data);
       if (result is! Map) {
         return null;
       }
       String id = result[Request.ID];
       String method = result[Request.METHOD];
       Map<String, Object> params = result[Request.PARAMS];
       Request request = new Request(id, method);
-      params.forEach((String key, Object value) {
-        request.setParameter(key, value);
-      });
+      if (params != null) {
+        params.forEach((String key, Object value) {
+          request.setParameter(key, value);
+        });
+      }
       return request;
     } catch (exception) {
       return null;
     }
   }
 
   /**
    * Return the value of the parameter with the given [name], or `null` if there
    * is no such parameter associated with this request.
    */
@@ skipping 398 matching lines @@
   /**
    * The response to be returned as a result of the failure.
    */
   final Response response;
 
   /**
    * Initialize a newly created exception to return the given reponse.
    */
   RequestFailure(this.response);
 }