TypeError: 'NoneType' object is not subscriptable

[sentry-io]

Sentry Issue: OPENVERSE-INGESTION_SERVER-17

TypeError: 'NoneType' object is not subscriptable
(1 additional frame(s) were not displayed)
...
  File "ingestion_server/tasks.py", line 261, in perform_task
    func()  # Run the task function if it is defined
  File "ingestion_server/tasks.py", line 250, in ingest_upstream
    indexer.reindex(model, f"temp_import_{model}", **kwargs)
  File "ingestion_server/indexer.py", line 280, in reindex
    schedule_distributed_index(
  File "ingestion_server/distributed_reindex_scheduler.py", line 34, in schedule_distributed_index
    _assign_work(db_conn, workers, model_name, table_name, target_index)
  File "ingestion_server/distributed_reindex_scheduler.py", line 43, in _assign_work
    estimated_records = cur.fetchone()[0]

'NoneType' object is not subscriptable

[AetherUnbound]

This exception occurred during local testing in an atypical scenario, closing.