build failure: `cannot coerce an integer to a string`

tried to update my flake from ba73719e673e7c2d89ac2f8df0bc0d48983e4907 to 62382bccfce7ddd67d7419fb90cc5b3cd437b17f i believe this is an oversight from #812? not sure relevant log output: ``` … while evaluating a path segment at /nix/store/366ad1aagjvy6aa82lcgl9s9xmmbi9gp-source/pkgs/buildCatppuccinPort/package.nix:22:85: 21| version = 22| args.version or ("0" + lib.optionalString (lastModified != null) "-unstable-${lastModified}"); | ^ 23| error: cannot coerce an integer to a string: 1769270365 ``` it failed on my invocation of a custom grub port, defined [here](https://github.com/w-lfchen/nixos-configs/blob/447b571a9eabede5afdfcc3d942dc07c55f92bb8/modules/nixos/boot.nix#L24). i'm not sure whether this is supported or the correct way to override sources, and all i remember from writing that code is that it took me a bit to find a working solution. fix should be straightforward, simply adding a `builtins.toString` should be enough if i'm not mistaken? i'll open a pr later if i find the time ``` nix repl Lix 2.96.0-dev-pre20260408-dev_bc9fb56 Type :? for help. nix-repl> "${5}" error: … while evaluating a path segment at «string»:1:3: 1| "${5}" | ^ error: cannot coerce an integer to a string: 5 nix-repl> "${builtins.toString 5}" "5" ``` lix version: ``` nix --version nix (Lix, like Nix) 2.96.0-dev-pre20260408-dev_bc9fb56 System type: x86_64-linux ```