Improve checking for older weather records

apps/openmw/mwworld/weather.cpp

@@ -725,7 +725,8 @@ bool WeatherManager::readRecord(ESM::ESMReader& reader, uint32_t type)
 {
     if(ESM::REC_WTHR == type)
     {
-        if(reader.getFormat() < ESM::SavedGame::sCurrentFormat)
+        static const int oldestCompatibleSaveFormat = 2;
+        if(reader.getFormat() < oldestCompatibleSaveFormat)
         {
             // Weather state isn't really all that important, so to preserve older save games, we'll just discard the
             // older weather records, rather than fail to handle the record.