use CodeGenModule::EmitNullConstant in a couple of places.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@77915 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGExprConstant.cpp b/lib/CodeGen/CGExprConstant.cpp
index dbb1bdc..3a1eac9 100644
--- a/lib/CodeGen/CGExprConstant.cpp
+++ b/lib/CodeGen/CGExprConstant.cpp
@@ -772,5 +772,5 @@
 llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) {
   // Always return an LLVM null constant for now; this will change when we
   // get support for IRGen of member pointers.
-  return llvm::Constant::getNullValue(getTypes().ConvertType(T));
+  return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T));
 }