[NFC][CLANG] [NFC][CLANG] Fix nullptr dereference issue in ConvertQualTypeToKind()

This patch uses castAs instead of getAs which will assert if the type doesn't match in ConvertQualTypeToKind(clang::ASTContext const &, clang::QualType).

Reviewed By: erichkeane

Differential Revision: https://reviews.llvm.org/D151928

Author: smanna12

clang/lib/Interpreter/Value.cpp

@@ -108,7 +108,7 @@ static Value::Kind ConvertQualTypeToKind(const ASTContext &Ctx, QualType QT) {
   if (!BT || BT->isNullPtrType())
     return Value::K_PtrOrObj;
 
-  switch (QT->getAs<BuiltinType>()->getKind()) {
+  switch (QT->castAs<BuiltinType>()->getKind()) {
   default:
     assert(false && "Type not supported");
     return Value::K_Unspecified;