Issue 3931. Visit children nodes safely.

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

Index: compiler/java/com/google/dart/compiler/ast/DartThrowStatement.java
diff --git a/compiler/java/com/google/dart/compiler/ast/DartThrowStatement.java b/compiler/java/com/google/dart/compiler/ast/DartThrowStatement.java
index 4797372252b2de2a340a82dadc66b2bb6daefdb6..fe71db7105f7ea5ac0f9a3167ab9391ee6e5ae9c 100644
--- a/compiler/java/com/google/dart/compiler/ast/DartThrowStatement.java
+++ b/compiler/java/com/google/dart/compiler/ast/DartThrowStatement.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.
 
@@ -26,9 +26,7 @@ public class DartThrowStatement extends DartStatement {
 
   @Override
   public void visitChildren(ASTVisitor<?> visitor) {
-    if (exception != null) {
-      exception.accept(visitor);
-    }
+    safelyVisitChild(exception, visitor);
   }
 
   @Override