Metadata is overwritten on thread update if not explicitly specified

[asvishnyakov]

Describe the bug

If metadata is None (which is default value) on update_thread, it will overwrite saved metadata with empty object

https://github.com/aitsc/chainlit/blob/31fe84a212f5a68fd0816f1e259d012c6cfa99e7/backend/chainlit/data/chainlit_data_layer.py#L551

[github-actions]

This issue is stale because it has been open for 14 days with no activity.

[asvishnyakov]

Still relevant

[github-actions]

This issue is stale because it has been open for 14 days with no activity.