Issue 3931. Visit children nodes safely.

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

Index: compiler/java/com/google/dart/compiler/ast/DartWhileStatement.java
diff --git a/compiler/java/com/google/dart/compiler/ast/DartWhileStatement.java b/compiler/java/com/google/dart/compiler/ast/DartWhileStatement.java
index f171fbbe9bd5510b5e1e72170acc88d53856fd7a..22d56dd4c80c7c5748e98d77023b013cf20a87c7 100644
--- a/compiler/java/com/google/dart/compiler/ast/DartWhileStatement.java
+++ b/compiler/java/com/google/dart/compiler/ast/DartWhileStatement.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.
 
@@ -27,8 +27,8 @@ public class DartWhileStatement extends DartStatement {
 
   @Override
   public void visitChildren(ASTVisitor<?> visitor) {
-    condition.accept(visitor);
-    body.accept(visitor);
+    safelyVisitChild(condition, visitor);
+    safelyVisitChild(body, visitor);
   }
 
   @Override