Fix for NPE in the server.

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:collection';
 import 'dart:convert';
 
 import 'package:analysis_server/src/computer/element.dart' show
@@ skipping 276 matching lines @@
       startLine,
       startColumn);
 }
 
 /**
  * Creates a new [Location] for the given [engine.Element].
  */
 Location _locationFromElement(engine.Element element) {
   engine.AnalysisContext context = element.context;
   engine.Source source = element.source;
+  if (context == null || source == null) {
+    return null;
+  }
   String name = element.displayName;
   int offset = element.nameOffset;
   int length = name != null ? name.length : 0;
   if (element is engine.CompilationUnitElement) {
     offset = 0;
     length = 0;
   }
   engine.SourceRange range = new engine.SourceRange(offset, length);
   return _locationForArgs(context, source, range);
 }
@@ skipping 637 matching lines @@
     hash = 0x1fffffff & (hash + ((0x03ffffff & hash) << 3));
     hash = hash ^ (hash >> 11);
     return 0x1fffffff & (hash + ((0x00003fff & hash) << 15));
   }
 
   static int hash2(a, b) => finish(combine(combine(0, a), b));
 
   static int hash4(a, b, c, d) =>
       finish(combine(combine(combine(combine(0, a), b), c), d));
 }