Fix user option

Author: thalin

modules/geth/default.nix

@@ -123,8 +123,8 @@ in {
                 baseServiceConfig
                 {
                   User =
-                    if cfg.user != null
-                    then cfg.user
+                    if cfg.args.user != null
+                    then cfg.args.user
                     else mkDefault serviceName;
                   StateDirectory = mkDefault serviceName;
                   ExecStart = mkDefault "${cfg.package}/bin/geth ${scriptArgs}";