make monster lights compatible with vanilla

Source/loadsave.cpp

@@ -625,7 +625,7 @@ void LoadMonster(LoadHelper *file, Monster &monster)
 	monster.leaderRelation = static_cast<LeaderRelation>(file->NextLE<uint8_t>());
 	monster.packsize = file->NextLE<uint8_t>();
 	monster.mlid = file->NextLE<int8_t>();
-	if (monster.mlid == Players[MyPlayerId]._plid)
+	if (monster.mlid == 0)
 		monster.mlid = NO_LIGHT; // Correct incorect values in old saves
 
 	if ((monster._mFlags & MFLAG_BERSERK) != 0) {
@@ -1305,7 +1305,11 @@ void SaveMonster(SaveHelper *file, Monster &monster)
 	file->WriteLE<uint8_t>(monster.leader);
 	file->WriteLE<uint8_t>(static_cast<std::uint8_t>(monster.leaderRelation));
 	file->WriteLE<uint8_t>(monster.packsize);
-	file->WriteLE<int8_t>(monster.mlid);
+	// vanilla compatibility
+	if (monster.mlid == NO_LIGHT)
+		file->WriteLE<int8_t>(0);
+	else
+		file->WriteLE<int8_t>(monster.mlid);
 
 	// Omit pointer mName;
 	// Omit pointer MType;