Connect UI doesn't accept empty strings for properties

[simplesteph]

I'm using the ElasticSearch connector. It seems it is not accepting the valid empty strings as a property which is valid java properties:

name=sink-elastic-twitter-distributed
connector.class=io.confluent.connect.elasticsearch.ElasticsearchSinkConnector
tasks.max=2
topics=demo-3-twitter
connection.url=http://elasticsearch:9200
type.name=kafka-connect
key.ignore=true
topic.key.ignore=
topic.index.map=
topic.schema.ignore=

Finally, if we don't specify them, the UI says they're required. but according to the doc at https://docs.confluent.io/3.3.0/connect/connect-elasticsearch/docs/configuration_options.html they're supposed to be optional. For example the quickstart config here: https://github.com/confluentinc/kafka-connect-elasticsearch/blob/master/config/quickstart-elasticsearch.properties does not specify them

Not sure if the issue lies with the connector itself, the framework, or the landoop image