Fix kernel/visitor_test

pkg/compiler/lib/src/ssa/kernel_impact.dart

Index: pkg/compiler/lib/src/ssa/kernel_impact.dart
diff --git a/pkg/compiler/lib/src/ssa/kernel_impact.dart b/pkg/compiler/lib/src/ssa/kernel_impact.dart
index c035c2d14c66d041e20b8d1484cd660c9351af4a..2bdc08d39aa03dfab3bd4ab5de18b07b321a0b09 100644
--- a/pkg/compiler/lib/src/ssa/kernel_impact.dart
+++ b/pkg/compiler/lib/src/ssa/kernel_impact.dart
@@ -107,11 +107,11 @@ class KernelImpactBuilder extends ir.Visitor {
     checkType(field.type);
     if (field.initializer != null) {
       visitNode(field.initializer);
-      if (!field.isInstanceMember && !field.isConst) {
+      if (!field.isInstanceMember &&
+          !field.isConst &&
+          field.initializer is! ir.NullLiteral) {
         impactBuilder.registerFeature(Feature.LAZY_FIELD);
       }
-    } else {
-      impactBuilder.registerFeature(Feature.FIELD_WITHOUT_INITIALIZER);
     }
     if (field.isInstanceMember && astAdapter.isNative(field.enclosingClass)) {
       impactBuilder