fix: account for None in error field of http response

Author: adrianAzoitei

trino/client.py

@@ -676,7 +676,7 @@ def process(self, http_response: Response) -> TrinoStatus:
 
         http_response.encoding = "utf-8"
         response = http_response.json()
-        if "error" in response:
+        if "error" in response and response["error"]:
             raise self._process_error(response["error"], response.get("id"))
 
         if constants.HEADER_CLEAR_SESSION in http_response.headers: