Using %(default)s inside square brackets crashes with ValueError

[hamdanal]

This program crashes with ValueError: substring not found

import argparse
from rich_argparse._argparse import RichHelpFormatter

parser = argparse.ArgumentParser(prog="PROG", formatter_class=RichHelpFormatter)
parser.add_argument("--hello", default="world", help="say hello to [default: %(default)s]")
parser.print_help()

Using square brackets here is wrong since it is considered markup but it shouldn't crash.