fix: websocket message handling

Author: Insmael

cryptomarket/websockets/market_data_client.py

@@ -35,7 +35,7 @@ def __init__(self, on_connect: Optional[Callable] = None, on_error: Optional[Cal
     def _handle(self, message):
         if 'ch' in message:
             self._handle_channel_feed(message)
-        if 'method' in message:
+        elif 'method' in message:
             self._handle_notification(message)
         elif 'id' in message:
             self._handle_response(message)