Don't use separate position field in /currency endpoint

freqtrade/wallets.py

@@ -118,8 +118,10 @@ class Wallets:
         for currency in deepcopy(self._wallets):
             if currency not in balances:
                 del self._wallets[currency]
+
         # TODO-lev: Implement dry-run/backtest counterpart
         positions = self._exchange.get_positions()
+        self._positions = []
         for position in positions:
             symbol = position['symbol']
             if position['side'] is None or position['collateral'] == 0.0: