Don't warn when matching %p to nullptr.

llvm-svn: 118344
diff --git a/clang/lib/Analysis/FormatString.cpp b/clang/lib/Analysis/FormatString.cpp
index 388b9d3..c1b5ea8 100644
--- a/clang/lib/Analysis/FormatString.cpp
+++ b/clang/lib/Analysis/FormatString.cpp
@@ -296,8 +296,8 @@
     }
 
     case CPointerTy:
-      return argTy->getAs<PointerType>() != NULL ||
-             argTy->getAs<ObjCObjectPointerType>() != NULL;
+      return argTy->isPointerType() || argTy->isObjCObjectPointerType() ||
+        argTy->isNullPtrType();
 
     case ObjCPointerTy:
       return argTy->getAs<ObjCObjectPointerType>() != NULL;