fix bug

py-client/sdk/trade.py

@@ -47,8 +47,10 @@ class TradeMixin:
         response = self._post_json(
             "/api/trade/ipo_data",
             {"type": str(ipo_type).strip().upper()},
-        ) or []
-        return response if isinstance(response, list) else []
+        )
+        if not isinstance(response, list):
+            raise ValueError('IPO response must be a list')
+        return response
 
 
     def cancel_by_id(self, order_id: str) -> dict[str, Any]: