UN-2980 [FIX] Handle null response (#1910)

UN-2980 Handle null response

Co-authored-by: harini-venkataraman <115449948+harini-venkataraman@users.noreply.github.com>

Author: Deepak-Kesavan

workers/executor/executors/answer_prompt.py

@@ -333,7 +333,7 @@ def handle_json(
             return
 
         parsed_data = repair_json_with_best_structure(answer)
-        if isinstance(parsed_data, str):
+        if not isinstance(parsed_data, (dict, list)):
             logger.error("Error parsing response to JSON")
             structured_output[prompt_key] = {}
             return