Issue 3931. Visit children nodes safely.

compiler/java/com/google/dart/compiler/ast/DartField.java

Index: compiler/java/com/google/dart/compiler/ast/DartField.java
diff --git a/compiler/java/com/google/dart/compiler/ast/DartField.java b/compiler/java/com/google/dart/compiler/ast/DartField.java
index a223d91a7bb84d051399e90ccfcbded9efccee09..654b770fc2b343cbfa5ccea5eb9516587aaa462d 100644
--- a/compiler/java/com/google/dart/compiler/ast/DartField.java
+++ b/compiler/java/com/google/dart/compiler/ast/DartField.java
@@ -1,4 +1,4 @@
-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
@@ -52,12 +52,8 @@ public class DartField extends DartClassMember<DartIdentifier> {
   @Override
   public void visitChildren(ASTVisitor<?> visitor) {
     super.visitChildren(visitor);
-    if (getAccessor() != null) {
-      getAccessor().accept(visitor);
-    }
-    if (getValue() != null) {
-      getValue().accept(visitor);
-    }
+    safelyVisitChild(accessor, visitor);
+    safelyVisitChild(value, visitor);
   }
 
   @Override