NixOS installation failed: Nightly 2021-12-19 is not available

[pca006132]

I tried to install the launcher using the command nix profile install github:veloren/Airshipper, but it failed with the message 'Nightly 2021-12-19 is not available'. Here is the trace:

error: Nightly 2021-12-19 is not available

       … while evaluating the attribute 'nightly."2021-12-19"'

       at /nix/store/knknkaha946ymfr4wmky7ic4ykwgrs0f-source/manifest.nix:111:7:

          110|       beta    = uncompressManifestSet "beta"    (import ./manifests/beta);
          111|       nightly = uncompressManifestSet "nightly" (import ./manifests/nightly);
             |       ^
          112|     };

       … while evaluating 'assertWith'

       at /nix/store/knknkaha946ymfr4wmky7ic4ykwgrs0f-source/rust-overlay.nix:14:29:

           13|
           14|     assertWith = cond: msg: body: if cond then body else throw msg;
             |                             ^
           15|

       … from call site

       at /nix/store/knknkaha946ymfr4wmky7ic4ykwgrs0f-source/rust-overlay.nix:43:7:

           42|     else if asNightlyDate != null then
           43|       assertWith (date == null) "Cannot specify date in both `channel` and `date`"
             |       ^
           44|         manifests.nightly.${asNightlyDate} or (throw "Nightly ${asNightlyDate} is not available")

       … while evaluating 'selectManifest'

       at /nix/store/knknkaha946ymfr4wmky7ic4ykwgrs0f-source/rust-overlay.nix:10:20:

            9|   # Manifest selector.
           10|   selectManifest = { channel, date ? null }: let
             |                    ^
           11|     inherit (self.rust-bin) manifests;

       … from call site

       at /nix/store/knknkaha946ymfr4wmky7ic4ykwgrs0f-source/rust-overlay.nix:56:44:

           55|       let
           56|         toolchain = toolchainFromManifest (selectManifest { inherit channel; });
             |                                            ^
           57|         profile' = if profile == null then "default" else profile;

       … while evaluating 'toolchainFromManifest'

       at /nix/store/knknkaha946ymfr4wmky7ic4ykwgrs0f-source/rust-overlay.nix:404:27:

          403|   #                       you will need to specify this extension in the extensions options or it will not be installed!
          404|   toolchainFromManifest = manifest: let
             |                           ^
          405|     inherit (builtins) elemAt;

       … from call site

       at /nix/store/knknkaha946ymfr4wmky7ic4ykwgrs0f-source/rust-overlay.nix:56:21:

           55|       let
           56|         toolchain = toolchainFromManifest (selectManifest { inherit channel; });
             |                     ^
           57|         profile' = if profile == null then "default" else profile;

       … while evaluating 'fromRustupToolchain'

       at /nix/store/knknkaha946ymfr4wmky7ic4ykwgrs0f-source/rust-overlay.nix:51:25:

           50|   # Or see source: https://github.com/rust-lang/rustup/blob/84974df1387812269c7b29fa5f3bb1c6480a6500/doc/src/overrides.md#the-toolchain-file
           51|   fromRustupToolchain = { path ? null, channel ? null, profile ? null, components ? [], targets ? [] }:
             |                         ^
           52|     if path != null then throw "`path` is not supported, please directly add it to your PATH instead"

       … from call site

       at /nix/store/knknkaha946ymfr4wmky7ic4ykwgrs0f-source/rust-overlay.nix:80:10:

           79|   in if legacy != null
           80|     then fromRustupToolchain { channel = head legacy; }
             |          ^
           81|     else fromRustupToolchain (fromTOML content).toolchain;

       … while evaluating 'fromRustupToolchainFile'

       at /nix/store/knknkaha946ymfr4wmky7ic4ykwgrs0f-source/rust-overlay.nix:75:29:

           74|   # Same as `fromRustupToolchain` but read from a `rust-toolchain` file (legacy one-line string or in TOML).
           75|   fromRustupToolchainFile = path: let
             |                             ^
           76|     inherit (builtins) readFile match fromTOML head;

       … from call site

       at /nix/store/kzgn1j3snzj7xra8x38481czxpf72y18-source/nixpkgs.nix:23:14:

           22|         if hasRustToolchainFile
           23|         then prev.rust-bin.fromRustupToolchainFile toolchainChannel
             |              ^
           24|         else prev.rust-bin.${toolchainChannel}.latest.default;

       … while evaluating the attribute 'RUSTC' of the derivation 'airshipper-0.7.0'

       at /nix/store/lf4nihr4qh32d3cqg75ivf818ji92q8k-source/pkgs/stdenv/generic/make-derivation.nix:203:11:

          202|         // (lib.optionalAttrs (attrs ? name || (attrs ? pname && attrs ? version)) {
          203|           name =
             |           ^
          204|             let