[clang] NFCI: Use FileEntryRef in ASTReader

Author: jansvoboda11

clang/lib/Serialization/ASTReader.cpp

@@ -5689,7 +5689,7 @@ llvm::Error ASTReader::ReadSubmoduleBlock(ModuleFile &F,
                                        "too many submodules");
 
       if (!ParentModule) {
-        if (const FileEntry *CurFile = CurrentModule->getASTFile()) {
+        if (OptionalFileEntryRef CurFile = CurrentModule->getASTFile()) {
           // Don't emit module relocation error if we have -fno-validate-pch
           if (!bool(PP.getPreprocessorOpts().DisablePCHOrModuleValidation &
                     DisableValidationForModuleKind::Module) &&