systemd.disallowedReferences: avoid `null`, really (#428280)

    lib.optionals (stdenv.buildPlatform != stdenv.hostPlatform)

      # 'or p' is for manually specified buildPackages as they dont have __spliced

      (

        builtins.map (p: p.__spliced.buildHost or p) (

          builtins.filter (p: p != null) finalAttrs.nativeBuildInputs

        builtins.filter (p: p != null) (

          builtins.map (p: p.__spliced.buildHost or p) finalAttrs.nativeBuildInputs

        )

      );