Do not emit InvalidStatement in sanitize_for_vm pass

pkg/kernel/lib/transformations/sanitize_for_vm.dart

Index: pkg/kernel/lib/transformations/sanitize_for_vm.dart
diff --git a/pkg/kernel/lib/transformations/sanitize_for_vm.dart b/pkg/kernel/lib/transformations/sanitize_for_vm.dart
index f5f86c357102d59d2aab0d294d29dcb6fe423bbd..fc83ab735362880aef337a05f49c0a7f84fad88c 100644
--- a/pkg/kernel/lib/transformations/sanitize_for_vm.dart
+++ b/pkg/kernel/lib/transformations/sanitize_for_vm.dart
@@ -14,7 +14,7 @@ class SanitizeForVM {
       for (var class_ in library.classes) {
         if (class_.constructors.isEmpty && class_.procedures.isEmpty) {
           class_.addMember(new Constructor(
-              new FunctionNode(new InvalidStatement()),
+              new FunctionNode(new EmptyStatement()),
               name: new Name('')));
         }
       }