Issue 3931. Visit children nodes safely.

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

Index: compiler/java/com/google/dart/compiler/ast/DartVariable.java
diff --git a/compiler/java/com/google/dart/compiler/ast/DartVariable.java b/compiler/java/com/google/dart/compiler/ast/DartVariable.java
index 94c2d6494e84401fc17b3d86e2a2155c46376993..491dd273c490f89ecb89707cb1da5a25e5e9421b 100644
--- a/compiler/java/com/google/dart/compiler/ast/DartVariable.java
+++ b/compiler/java/com/google/dart/compiler/ast/DartVariable.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.
 
@@ -42,9 +42,7 @@ public class DartVariable extends DartDeclaration<DartIdentifier> {
   @Override
   public void visitChildren(ASTVisitor<?> visitor) {
     super.visitChildren(visitor);
-    if (value != null) {
-      value.accept(visitor);
-    }
+    safelyVisitChild(value, visitor);
   }
 
   @Override