Fix Kraken balance update error

closes #4873

freqtrade/exchange/kraken.py

@@ -53,6 +53,8 @@ class Kraken(Exchange):
                            # x["side"], x["amount"],
                            ) for x in orders]
             for bal in balances:
+                if not isinstance(balances[bal], dict):
+                    continue
                 balances[bal]['used'] = sum(order[1] for order in order_list if order[0] == bal)
                 balances[bal]['free'] = balances[bal]['total'] - balances[bal]['used']
 

tests/exchange/test_kraken.py

@@ -90,6 +90,7 @@ def test_get_balances_prod(default_conf, mocker):
         '3ST': balance_item.copy(),
         '4ST': balance_item.copy(),
         'EUR': balance_item.copy(),
+        'timestamp': 123123
     })
     kraken_open_orders = [{'symbol': '1ST/EUR',
                            'type': 'limit',
@@ -138,7 +139,7 @@ def test_get_balances_prod(default_conf, mocker):
     default_conf['dry_run'] = False
     exchange = get_patched_exchange(mocker, default_conf, api_mock, id="kraken")
     balances = exchange.get_balances()
-    assert len(balances) == 5
+    assert len(balances) == 6
 
     assert balances['1ST']['free'] == 9.0
     assert balances['1ST']['total'] == 10.0