Empty string with completion type results in IllegalArgumentException

[bjfish]

Elasticsearch version:
5.2.0

Description of the problem including expected versus actual behavior:

Result is IllegalArgumentException. Expected empty strings to be ignored.

Is this an issue? If not, is there a recommended resolution?

Steps to reproduce:
In Sense:

PUT twitter
{
  "mappings": {
    "tweet": {
      "properties": {
        "message": {
          "type": "completion"
        }
      }
    }
  }
}

PUT twitter/tweet/3
{
    "message" : ""
}

Edit: Updated description to simpler example.

[clintongormley]

I agree - empty string should be ignored.

Simpler recreation:

PUT twitter
{
  "mappings": {
    "tweet": {
      "properties": {
        "message": {
          "type": "completion"
        }
      }
    }
  }
}

PUT twitter/tweet/3
{
    "message" : ""
}

[floflock]

Have the same issue. Does anyone have a solution for that?

[andyb-elastic]

@elastic/es-search-aggs

Jim has a PR open for this #28289