unable to set theme without colors key in alacritty.yaml

[cherepanov]

Traceback (most recent call last):
  File "/home/ac/.local/bin/alacritty-colorscheme", line 8, in <module>
    sys.exit(main())
  File "/home/ac/.local/lib/python3.10/site-packages/alacritty_colorscheme/cli.py", line 158, in main
    handle_args(args)
  File "/home/ac/.local/lib/python3.10/site-packages/alacritty_colorscheme/cli.py", line 147, in handle_args
    replace_colorscheme(colors_path, args.config_file,
  File "/home/ac/.local/lib/python3.10/site-packages/alacritty_colorscheme/colorscheme.py", line 72, in replace_colorscheme
    config_yaml['colors'].update(colors_yaml['colors'])
TypeError: 'NoneType' object is not subscriptable