text: Title: error of processing all videos in upload folder
  Body: when running
  `!python inference_realesrgan_video.py --input upload -n RealESRGANv2-animevideo-xsx2 -s 4 -v -a --half --suffix outx2
  `
  I'm getting :
  
  ```
  Traceback (most recent call last):
    File "inference_realesrgan_video.py", line 199, in <module>
      main()
    File "inference_realesrgan_video.py", line 108, in main
      if mimetypes.guess_type(args.input)[0].startswith('video'):  # is a video file
  AttributeError: 'NoneType' object has no attribute 'startswith'
  
  
  ```
  I'm unable to run the inference on the videos inside the upload folder one after the other.
  
  Hope someone can help fix this issue.