[NFC][CLANG] Fix nullptr dereference issue in SetValueDataBasedOnQual…

…Type()

This patch uses castAs instead of getAs which will assert if the type doesn't match in SetValueDataBasedOnQualType(clang::Value &, unsigned long long).

Reviewed By: erichkeane

Differential Revision: https://reviews.llvm.org/D151770

clang/lib/Interpreter/Interpreter.cpp

@@ -768,7 +768,7 @@ static void SetValueDataBasedOnQualType(Value &V, unsigned long long Data) {
   if (const auto *ET = QT->getAs<EnumType>())
     QT = ET->getDecl()->getIntegerType();
 
-  switch (QT->getAs<BuiltinType>()->getKind()) {
+  switch (QT->castAs<BuiltinType>()->getKind()) {
   default:
     llvm_unreachable("unknown type kind!");
 #define X(type, name)                                                          \