Add default null value

Signed-off-by: Marin <[email protected]>

Author: supermarin

flake.nix

@@ -95,6 +95,7 @@
 
           tailscaleAuthKeyFile = mkOption {
             type = types.nullOr types.path;
+            default = null;
             description = "Path to file containing the Tailscale Auth Key";
           };