margin_mode is empty string for spot new configs

freqtrade/commands/build_config_commands.py

@@ -207,7 +207,7 @@ def ask_user_config() -> Dict[str, Any]:
         # Interrupted questionary sessions return an empty dict.
         raise OperationalException("User interrupted interactive questions.")
     answers["margin_mode"] = (
-        '\n    "margin_mode": "isolated",'
+        'isolated'
         if answers.get("trading_mode") == 'futures'
         else ''
     )

freqtrade/templates/base_config.json.j2

@@ -13,7 +13,8 @@
     "fiat_display_currency": "{{ fiat_display_currency }}",{{ ('\n    "timeframe": "' + timeframe + '",') if timeframe else '' }}
     "dry_run": {{ dry_run | lower }},
     "cancel_open_orders_on_exit": false,
-    "trading_mode": "{{ trading_mode }}",{{ margin_mode }}
+    "trading_mode": "{{ trading_mode }}",
+    "margin_mode": "{{ margin_mode }}",
     "unfilledtimeout": {
         "buy": 10,
         "sell": 10,