Fix for invalidating results of a target being removed.

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

Index: pkg/analyzer/lib/src/context/cache.dart
diff --git a/pkg/analyzer/lib/src/context/cache.dart b/pkg/analyzer/lib/src/context/cache.dart
index ded58c9b5c44dbd1e13a218b6ab6a99220122286..fa7bf4834b2a31ac74d3bf7dd43fd0a300a6faee 100644
--- a/pkg/analyzer/lib/src/context/cache.dart
+++ b/pkg/analyzer/lib/src/context/cache.dart
@@ -453,7 +453,9 @@ class CacheEntry {
     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) {