Implement second part of PR 2600: NSError** parameter may be null, and should be checked before being dereferenced.

llvm-svn: 56318
diff --git a/clang/lib/Analysis/BasicValueFactory.cpp b/clang/lib/Analysis/BasicValueFactory.cpp
index 8d737a9..a9bb2ce 100644
--- a/clang/lib/Analysis/BasicValueFactory.cpp
+++ b/clang/lib/Analysis/BasicValueFactory.cpp
@@ -247,3 +247,8 @@
   return P->getValue();
 }
 
+const RVal* BasicValueFactory::getPersistentRVal(RVal X) {
+  return &getPersistentRValWithData(X, 0).first;
+}  
+
+