Removed the unused ParseMonsterIdIfNotEmpty() function

Source/monstdat.cpp

@@ -233,15 +233,6 @@ tl::expected<_monster_id, std::string> ParseMonsterId(std::string_view value)
 	return tl::make_unexpected("Unknown enum value");
 }
 
-tl::expected<_monster_id, std::string> ParseMonsterIdIfNotEmpty(std::string_view value)
-{
-	if (value.empty()) {
-		return MT_INVALID;
-	}
-
-	return ParseMonsterId(value);
-}
-
 tl::expected<MonsterAvailability, std::string> ParseMonsterAvailability(std::string_view value)
 {
 	if (value == "Always") return MonsterAvailability::Always;