Don't reset open-order-id just yet

it's needed to get the fees

freqtrade/freqtradebot.py

@@ -606,7 +606,6 @@ class FreqtradeBot:
                 stake_amount = order['cost']
                 amount = safe_value_fallback(order, 'filled', 'amount')
                 buy_limit_filled_price = safe_value_fallback(order, 'average', 'price')
-                order_id = None
 
         # in case of FOK the order may be filled immediately and fully
         elif order_status == 'closed':

tests/test_freqtradebot.py

@@ -1057,7 +1057,7 @@ def test_execute_buy(mocker, default_conf, fee, limit_buy_order, limit_buy_order
     assert freqtrade.execute_buy(pair, stake_amount)
     trade = Trade.query.all()[3]
     assert trade
-    assert trade.open_order_id is None
+    assert trade.open_order_id == '555'
     assert trade.open_rate == 0.5
     assert trade.stake_amount == 40.495905365