Guard against null in EditDomain.

pkg/analysis_server/lib/src/analysis_server.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 analysis.server;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:core';
 import 'dart:io' as io;
@@ skipping 312 matching lines @@
   nd.PerformanceLog _analysisPerformanceLogger;
   ByteStore byteStore;
   nd.AnalysisDriverScheduler analysisDriverScheduler;
 
   /**
    * The set of the files that are currently priority.
    */
   final Set<String> priorityFiles = new Set<String>();
 
   /**
-   * The cached results units for [priorityFiles].
+   * The cached results for [priorityFiles].
+   * These results must have not `null` units.
    */
   final Map<String, nd.AnalysisResult> priorityFileResults = {};
 
   /**
    * Initialize a newly created server to receive requests from and send
    * responses to the given [channel].
    *
    * If [rethrowExceptions] is true, then any exceptions thrown by analysis are
    * propagated up the call stack.  The default is true to allow analysis
    * exceptions to show up in unit tests, but it should be set to false when
@@ skipping 1462 matching lines @@
         resourceProvider,
         analysisServer.byteStore,
         analysisServer.fileContentOverlay,
         sourceFactory,
         analysisOptions);
     analysisDriver.name = folder.shortName;
     analysisDriver.status.listen((status) {
       // TODO(scheglov) send server status
     });
     analysisDriver.results.listen((result) {
-      if (analysisServer.priorityFiles.contains(result.path)) {
+      if (analysisServer.priorityFiles.contains(result.path) &&
+          result.unit != null) {
         analysisServer.priorityFileResults[result.path] = result;
       }
       _runDelayed(() {
         new_sendErrorNotification(analysisServer, result);
       });
       String path = result.path;
       CompilationUnit unit = result.unit;
       if (unit != null) {
         if (analysisServer._hasAnalysisServiceSubscription(
             AnalysisService.HIGHLIGHTS, path)) {
@@ skipping 256 matching lines @@
    */
   static PerformanceTag splitStore = new PerformanceTag('splitStore');
 }
 
 class _NullStringSink implements StringSink {
   void write(Object obj) {}
   void writeAll(Iterable objects, [String separator = ""]) {}
   void writeCharCode(int charCode) {}
   void writeln([Object obj = ""]) {}
 }