kup crashes when no nix profile installs exist

[goodlyrottenapple]

Fix

kup git:(develop) kup install k
Traceback (most recent call last):
  File "/usr/local/bin/kup", line 8, in <module>
    sys.exit(main())
  File "/usr/local/lib/python3.9/site-packages/kup/__main__.py", line 306, in main
    install_package(args.package, args.version)
  File "/usr/local/lib/python3.9/site-packages/kup/__main__.py", line 208, in install_package
    reload_packages()
  File "/usr/local/lib/python3.9/site-packages/kup/__main__.py", line 105, in reload_packages
    with open(f'{os.getenv("HOME")}/.nix-profile/manifest.json') as manifest_file:
FileNotFoundError: [Errno 2] No such file or directory: '/Users/brucecollie/.nix-profile/manifest.json'