Vim themes in home.nix

I seem to have messed up my configuration and can’t see how to fix it. I had home.nix configured with:

programs.vim = {
  enable = true;
  plugins = with pkgs.vimPlugins; [ dracula-vim ];
  extraConfig = ''
    colorscheme dracula

It worked fine, but didn’t look right, so I followed the instructions here which installed the theme in ~/.vim/pack/themes/start. It looked the same as the first one, do I deleted that folder and tried to get the plugin theme working again. Now, when I open vim, I get this:

Error detected while processing /nix/store/hash-vimrc[12]../nix/store/hash-vimplugin-dracula-vim-2021-10-23/colors/dracula.vim:

followed by a bunch of “undefined variable” errors. It seems like I deleted something I shouldn’t have. How can I reset/fix my vim config?

Have you tried rolling nix back?