fix(realtime): use pop with default in _handle_message to prevent KeyError (#1388)

Author: SmaugPool

src/realtime/src/realtime/_async/channel.py

@@ -525,7 +525,7 @@ def _handle_message(self, message: ServerMessage):
                 self.on_error(dict(message.payload))
         elif isinstance(message, ReplyMessage):
             reply_payload = message.payload
-            if message.ref and (push := self.messages_waiting_for_ack.pop(message.ref)):
+            if message.ref and (push := self.messages_waiting_for_ack.pop(message.ref, None)):
                 if reply_payload.status == "ok":
                     push.trigger(
                         RealtimeAcknowledgementStatus.Ok, reply_payload.response