Fix kernel/visitor_test

pkg/compiler/lib/src/resolution/resolution.dart

Index: pkg/compiler/lib/src/resolution/resolution.dart
diff --git a/pkg/compiler/lib/src/resolution/resolution.dart b/pkg/compiler/lib/src/resolution/resolution.dart
index 09ef8f902c1c07bf737080643d09ee7d7525b19b..ebea1afdba68b8cc09c5f32ed7c5f7f1fe9f376b 100644
--- a/pkg/compiler/lib/src/resolution/resolution.dart
+++ b/pkg/compiler/lib/src/resolution/resolution.dart
@@ -425,7 +425,8 @@ class ResolverTask extends CompilerTask {
           }
         });
         if (initializer != null) {
-          if (!element.modifiers.isConst) {
+          if (!element.modifiers.isConst &&
+              initializer.asLiteralNull() == null) {
             // TODO(johnniwinther): Determine the const-ness eagerly to avoid
             // unnecessary registrations.
             registry.registerFeature(Feature.LAZY_FIELD);