Issue 3931. Visit children nodes safely.

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

Index: compiler/java/com/google/dart/compiler/ast/DartMethodInvocation.java
diff --git a/compiler/java/com/google/dart/compiler/ast/DartMethodInvocation.java b/compiler/java/com/google/dart/compiler/ast/DartMethodInvocation.java
index 68403b796177a29e841f1e0a960a6efbbacc92cd..8ae56d09cfbe00446f97f489b28f01fbb20d6350 100644
--- a/compiler/java/com/google/dart/compiler/ast/DartMethodInvocation.java
+++ b/compiler/java/com/google/dart/compiler/ast/DartMethodInvocation.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.
 
@@ -63,8 +63,8 @@ public class DartMethodInvocation extends DartInvocation {
 
   @Override
   public void visitChildren(ASTVisitor<?> visitor) {
-    target.accept(visitor);
-    functionName.accept(visitor);
+    safelyVisitChild(target, visitor);
+    safelyVisitChild(functionName, visitor);
     visitor.visit(getArguments());
   }