python3Packages.ray: re-add empty set fallback

[zowoq]

Now that nixpkgs recurses into python313 this has broken https://github.com/nix-community/nixpkgs-update-github-releases. It would be better to handle to try and handle these cases in nixpkgs-update-github-releases but for now I'd like to merge this to unblock package updates.

error:
        … while calling the 'listToAttrs' builtin
          at /nix/store/cpgc7nj9axliidxbqk9wm5kcxv1v4xc0-source/loadMetaFromPath.nix:42:3:
            41| in
            42|   pkgs.lib.listToAttrs filtered
              |   ^
            43|
        … while calling the 'filter' builtin
          at /nix/store/cpgc7nj9axliidxbqk9wm5kcxv1v4xc0-source/loadMetaFromPath.nix:40:14:
            39|     (pkgs.lib.splitString "\n" (pkgs.lib.fileContents universeFile));
            40|   filtered = pkgs.lib.filter (x: x != null) versions;
              |              ^
            41| in
        (stack trace truncated; use '--show-trace' to show the full, detailed trace)
        error: attribute 'cp313' missing
        at /nix/store/6jgvs97718i2c81f8dyldglpc3hf49xi-source/pkgs/development/python-modules/ray/default.nix:90:14:
            89|       platform = "manylinux2014_x86_64";
            90|       hash = binary-hashes.${pyShortVersion};
              |              ^
            91|     };
        Did you mean one of cp310, cp311 or cp312?

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 25.05 Release Notes (or backporting 24.11 and 25.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[GaetanLepage]

nixpkgs-review result

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Command: nixpkgs-review pr 367782

[zowoq]

Thanks!