Handle empty-history case in mark_last_wftask_as_failed

fractal_server/app/runner/v2/handle_failed_job.py

@@ -36,6 +36,13 @@ def mark_last_wftask_as_failed(
     logger = logging.getLogger(logger_name)
     with next(get_sync_db()) as db:
         db_dataset = db.get(DatasetV2, dataset_id)
+        if len(db_dataset.history) == 0:
+            logger.warning(
+                f"History for {dataset_id=} is empty. Likely reason: the job "
+                "failed before its first task was marked as SUBMITTED. "
+                "Continue."
+            )
+            return
         workflowtask_id = db_dataset.history[-1]["workflowtask"]["id"]
         last_item_status = db_dataset.history[-1]["status"]
         if last_item_status != WorkflowTaskStatusTypeV2.SUBMITTED: