[BUG] Elastic pipeline errors on empty `text` field

[olivernormand]

Bug Description

When documents are uploaded to Elastic, they can fall over if the text field is empty. This can often take down the entire batch of documents

Steps to Reproduce

1. Generate some documents with an empty text field
2. Upload to elastic
3. See error

Expected vs Actual Behavior

• Expected: They should fail gracefully, with the remaining documents still being uploaded
• Actual: The whole batch fails