Don't replace empty strain names

ingest/config/defaults.yaml

@@ -65,7 +65,7 @@ curate:
   # Currently accepts any characters because we do not have a clear standard for strain names across pathogens
   strain_regex: '^.+$'
   # Back up strain name field to use if 'strain' doesn't match regex above
-  strain_backup_fields: ['accession']
+  strain_backup_fields: []
   # List of date fields to standardize to ISO format YYYY-MM-DD
   date_fields: ['date', 'date_released', 'date_updated']
   # List of expected date formats that are present in the date fields provided above