fix configFilesPath

Author: brainrake

modules/block-producer-node/default.nix

@@ -28,8 +28,9 @@ in
         };
 
         configFilesPath = lib.mkOption {
-          type = lib.types.path;
-          description = "Path to the network configuration directory";
+          type = lib.types.nullOr lib.types.path;
+	        default = null;
+          description = "Path to the network configuration directory. Optional, will use cardano-node service configuration if set to null.";
         };
       };
     };
@@ -45,9 +46,11 @@ in
       services.cardano-node = mkMerge [
         {
           enable = true;
+        }
+	      (mkIf (cfg.configFilesPath != null) {
           nodeConfigFile = "${cfg.configFilesPath}/configuration.yaml";
           topology = "${cfg.configFilesPath}/topology-spo-1.json";
-        }
+        })
         (mkIf (cfg.block-producer-key-path != null) {
           signingKey = "${cfg.block-producer-key-path}/byron-gen-command/delegate-keys.000.key";
           delegationCertificate = "${cfg.block-producer-key-path}/byron-gen-command/delegation-cert.000.json";