Issue 3931. Visit children nodes safely.

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

Index: compiler/java/com/google/dart/compiler/ast/DartFunctionTypeAlias.java
diff --git a/compiler/java/com/google/dart/compiler/ast/DartFunctionTypeAlias.java b/compiler/java/com/google/dart/compiler/ast/DartFunctionTypeAlias.java
index 152133b2c59107c5a22ad7f6da92f5af7bbb6813..e5b24234322240401d3294ce6950c785210dbf83 100644
--- a/compiler/java/com/google/dart/compiler/ast/DartFunctionTypeAlias.java
+++ b/compiler/java/com/google/dart/compiler/ast/DartFunctionTypeAlias.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.
 
@@ -57,9 +57,7 @@ public class DartFunctionTypeAlias extends DartDeclaration<DartIdentifier> {
   @Override
   public void visitChildren(ASTVisitor<?> visitor) {
     super.visitChildren(visitor);
-    if (returnTypeNode != null) {
-      returnTypeNode.accept(visitor);
-    }
+    safelyVisitChild(returnTypeNode, visitor);
     parameters.accept(visitor);
     typeParameters.accept(visitor);
   }