more pr feedback

src/js_realm.hpp

@@ -248,7 +248,7 @@ inline typename T::Function RealmClass<T>::create_constructor(ContextType ctx) {
 }
     
 static inline void convert_outdated_datetime_columns(const SharedRealm &realm) {
-    int old_file_format_version = realm->file_format_upgraded_from_version();
+    realm::util::Optional<int> old_file_format_version = realm->file_format_upgraded_from_version();
     if (old_file_format_version && old_file_format_version < 5) {
         // any versions earlier than file format 5 are stored as milliseconds and need to be converted to the new format
         for (auto& object_schema : *realm->config().schema) {

src/object-store/src/shared_realm.cpp

@@ -463,10 +463,10 @@ void Realm::close()
     m_coordinator = nullptr;
 }
 
-int Realm::file_format_upgraded_from_version() const
+util::Optional<int> Realm::file_format_upgraded_from_version() const
 {
     if (upgrade_initial_version != upgrade_final_version) {
         return upgrade_initial_version;
     }
-    return 0;
+    return util::Optional<int>();
 }

src/object-store/src/shared_realm.hpp

@@ -133,7 +133,7 @@ namespace realm {
         void close();
 
         // returns the file format version upgraded from, or 0 if not upgraded
-        int file_format_upgraded_from_version() const;
+        util::Optional<int> file_format_upgraded_from_version() const;
 
         ~Realm();