text: Title: TypeError: cannot unpack non-iterable NoneType object
  Body: ## generating video: 1 => ./storage/tasks/a240439d-b011-484d-8aa8-a223665691ee/final-1.mp4
  2024-04-12 16:01:33 | INFO | "./app/services/video.py:183": generate_video - start, video size: 1080 x 1920
  2024-04-12 16:01:33 | INFO | "./app/services/video.py:184": generate_video -   ① video: ./storage/tasks/a240439d-b011-484d-8aa8-a223665691ee/combined-1.mp4
  2024-04-12 16:01:33 | INFO | "./app/services/video.py:185": generate_video -   ② audio: ./storage/tasks/a240439d-b011-484d-8aa8-a223665691ee/audio.mp3
  2024-04-12 16:01:33 | INFO | "./app/services/video.py:186": generate_video -   ③ subtitle: ./storage/tasks/a240439d-b011-484d-8aa8-a223665691ee/subtitle.srt
  2024-04-12 16:01:33 | INFO | "./app/services/video.py:187": generate_video -   ④ output: ./storage/tasks/a240439d-b011-484d-8aa8-a223665691ee/final-1.mp4
  2024-04-12 16:01:33 | INFO | "./app/services/video.py:202": generate_video - using font: ./resource/fonts/STHeitiLight.ttc
  2024-04-12 16:01:34.052 Uncaught app exception
  Traceback (most recent call last):
    File "/opt/anaconda3/envs/MoneyPrinterTurbo/lib/python3.10/site-packages/streamlit/runtime/scriptrunner/script_runner.py", line 542, in _run_script
      exec(code, module.__dict__)
    File "/Users/xunuoqing/Downloads/MoneyPrinterTurbo-main/webui/Main.py", line 432, in <module>
      result = tm.start(task_id=task_id, params=params)
    File "/Users/xunuoqing/Downloads/MoneyPrinterTurbo-main/app/services/task.py", line 155, in start
      video.generate_video(video_path=combined_video_path,
    File "/Users/xunuoqing/Downloads/MoneyPrinterTurbo-main/app/services/video.py", line 238, in generate_video
      sub = SubtitlesClip(subtitles=subtitle_path, encoding='utf-8')
    File "/opt/anaconda3/envs/MoneyPrinterTurbo/lib/python3.10/site-packages/moviepy/video/tools/subtitles.py", line 69, in __init__
      self.duration = max([tb for ((ta, tb), txt) in self.subtitles])
    File "/opt/anaconda3/envs/MoneyPrinterTurbo/lib/python3.10/site-packages/moviepy/video/tools/subtitles.py", line 69, in <listcomp>
      self.duration = max([tb for ((ta, tb), txt) in self.subtitles])
  TypeError: cannot unpack non-iterable NoneType object
  
  
  [audio.mp3.json](https://github.com/harry0703/MoneyPrinterTurbo/files/14956044/audio.mp3.json)
  [script.json](https://github.com/harry0703/MoneyPrinterTurbo/files/14956045/script.json)
  [subtitle.srt.json](https://github.com/harry0703/MoneyPrinterTurbo/files/14956046/subtitle.srt.json)
  