Don't disable an aggregation with a single option

It could make sense to select the single option of an aggregation as all documents might not have this field with a value (for example, a search returning 250 documents, but a domain aggregation with only Plant [5] as a possibility).

It would be better to allow to select it. Check to see if we can offer a "No value" option to filter the documents with no value in this field. see #3 (closed)