Use the right cast kind when comparing null to member pointers.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@79927 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 59502c4..d9add06 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -4292,13 +4292,13 @@
     if (RHSIsNull && 
         (lType->isPointerType() ||
          (!isRelational && lType->isMemberPointerType()))) {
-      ImpCastExprToType(rex, lType);
+      ImpCastExprToType(rex, lType, CastExpr::CK_NullToMemberPointer);
       return ResultTy;
     }
     if (LHSIsNull &&
         (rType->isPointerType() ||
          (!isRelational && rType->isMemberPointerType()))) {
-      ImpCastExprToType(lex, rType);
+      ImpCastExprToType(lex, rType, CastExpr::CK_NullToMemberPointer);
       return ResultTy;
     }