How to add a dummy chunk if the live stream stops...or gets corrupted

Hi all!!
how can i addd a dummy segmenet/chunk in the m3u8 file.
i am using ffmpeg with python but stuck on this issue …

what if the stream is not comming how can i add a dummy chunks until it starts again
so that the length of m3u8 file does not get effected (i run the live stream at 10:00AM and stream stops at 10:30AM not the command should start adding dummy chunks and when i watch the m3u8 file after 3 hours its length should be 3 hours in which 30 minutes video will be of stream wile the other part consist of dummy chunks)

here is my code:
ffmpeg_command = [
“-i”, input_url,
“-c:v”, “libx264”,
“-g”, “50”,
“-f”, “hls”,
“-crf”, “30”,
“-hls_time”, “5”,
“-hls_list_size”, “0”,
“-hls_segment_filename”, os.path.join(todayStreamDirectory, ‘%d.ts’),
“-hls_flags”, “append_list”,