CGExprConstant - silence static analyzer getAs<> null dereference warning. NFCI.

The static analyzer is warning about a potential null dereference, but in these cases we should be able to use castAs<> directly and if not assert will fire for us.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@374988 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGExprConstant.cpp b/lib/CodeGen/CGExprConstant.cpp
index 03ef4ab..96e8c9c 100644
--- a/lib/CodeGen/CGExprConstant.cpp
+++ b/lib/CodeGen/CGExprConstant.cpp
@@ -1269,8 +1269,8 @@
       return nullptr;
 
     // FIXME: We should not have to call getBaseElementType here.
-    const RecordType *RT =
-      CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>();
+    const auto *RT =
+        CGM.getContext().getBaseElementType(Ty)->castAs<RecordType>();
     const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
 
     // If the class doesn't have a trivial destructor, we can't emit it as a