Avoid crashing on function syntax.

pkg/front_end/lib/src/fasta/source/stack_listener.dart

Index: pkg/front_end/lib/src/fasta/source/stack_listener.dart
diff --git a/pkg/front_end/lib/src/fasta/source/stack_listener.dart b/pkg/front_end/lib/src/fasta/source/stack_listener.dart
index 97938777fc551813e5f56bac370aa3e2fe41f285..3f48e82f9fde5d82d94fe72687c595903bced59a 100644
--- a/pkg/front_end/lib/src/fasta/source/stack_listener.dart
+++ b/pkg/front_end/lib/src/fasta/source/stack_listener.dart
@@ -33,6 +33,7 @@ enum NullValue {
   FunctionBody,
   FunctionBodyAsyncToken,
   FunctionBodyStarToken,
+  Identifier,
   IdentifierList,
   Initializers,
   Metadata,
@@ -113,6 +114,12 @@ abstract class StackListener extends Listener {
   }
 
   @override
+  void handleNoName(Token token) {
+    debugEvent("NoName");
+    push(NullValue.Identifier);
+  }
+
+  @override
   void endInitializer(Token token) {
     debugEvent("Initializer");
   }