Protect against KeyError on balanceUpdate

Got a report for KeyError on del balances with 'LDDOGE' as key, apparently this key doesn't correspond to any known spot asset and it should be safe to ignore such asset updates

(cherry picked from commit c96b553)

binance_trade_bot/binance_stream_manager.py

@@ -149,7 +149,9 @@ def _process_stream_data(self, stream_data):
         elif event_type == "balanceUpdate":  # !userData
             self.logger.debug(f"Balance update: {stream_data}")
             with self.cache.open_balances() as balances:
-                del balances[stream_data["asset"]]
+                asset = stream_data["asset"]
+                if asset in balances:
+                    del balances[stream_data["asset"]]
         elif event_type in ("outboundAccountPosition", "outboundAccountInfo"):  # !userData
             self.logger.debug(f"{event_type}: {stream_data}")
             with self.cache.open_balances() as balances: