Fix for invalidating results of a target being removed.

pkg/analyzer/lib/src/context/cache.dart

 // Copyright (c) 2015, 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 analyzer.src.context.cache;
 
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/engine.dart'
     show AnalysisEngine, CacheState, InternalAnalysisContext, RetentionPriority;
@@ skipping 435 matching lines @@
       ResultData data = _partition._getDataFor(dependedOnResult, orNull: true);
       if (data != null) {
         data.dependentResults.remove(thisResult);
       }
     });
     // Invalidate results that depend on this result.
     List<TargetedResult> dependentResults = thisData.dependentResults;
     thisData.dependentResults = <TargetedResult>[];
     dependentResults.forEach((TargetedResult dependentResult) {
       CacheEntry entry = _partition.get(dependentResult.target);
-      entry._invalidate(dependentResult.result, true);
+      if (entry != null) {
+        entry._invalidate(dependentResult.result, true);
+      }
     });
     // If empty, remove the entry altogether.
     if (_resultMap.isEmpty) {
       _partition._targetMap.remove(target);
     }
   }
 
   /**
    * Invalidates all the results of this entry, with propagation.
    */
@@ skipping 465 matching lines @@
 class UniversalCachePartition extends CachePartition {
   /**
    * Initialize a newly created cache partition, belonging to the given
    * [context].
    */
   UniversalCachePartition(InternalAnalysisContext context) : super(context);
 
   @override
   bool isResponsibleFor(AnalysisTarget target) => true;
 }