Check that AnalysisContext is not null.

pkg/analysis_server/lib/src/services/index/store/split_store.dart

Index: pkg/analysis_server/lib/src/services/index/store/split_store.dart
diff --git a/pkg/analysis_server/lib/src/services/index/store/split_store.dart b/pkg/analysis_server/lib/src/services/index/store/split_store.dart
index eed774fd90d287e2e26c0539be416c4d9c72c421..880cad3a82c51bb38bac844567fa88580e64a08c 100644
--- a/pkg/analysis_server/lib/src/services/index/store/split_store.dart
+++ b/pkg/analysis_server/lib/src/services/index/store/split_store.dart
@@ -813,7 +813,7 @@ class SplitIndexStore implements InternalIndexStore {
 
   @override
   bool aboutToIndex(AnalysisContext context, Object object) {
-    if (context.isDisposed) {
+    if (context == null || context.isDisposed) {

[Brian Wilkerson, 2015/10/19 19:57:03]

I'm concerned that we're masking a deeper bug. Could we add an assert statement
here, or log information about what happened (although if it's happening a lot
that could negatively impact instrumentation)?

[scheglov, 2015/10/19 20:25:46]

We're definitely are masking a bug here.
But for now I'm more concerned about fixing the problem.

I've opened a new issue to track the problem.
https://github.com/dart-lang/sdk/issues/24629

       return false;
     }
     // try to find a node name