关于suggest下搜索一个不存在的分词报错的问题

es6.8

POST /suggest_master/model/_search
{
"_source": {
"includes": [
"topicdesc",
"modeldesc"
],
"excludes":
},
"suggest": {
"modeldesc": {
"text": "宝马",
"completion": {
"field": "modeldesc.ik",
"size": 10
}
},
"topicdesc": {
"text": "宝马",
"completion": {
"field": "topicdesc.ik",
"size": 10
}
}
}
}
报错信息:
{
  "error": {
    "root_cause": [
      {
        "type": "null_pointer_exception",
        "reason": null
      }
    ],
    "type": "search_phase_execution_exception",
    "reason": "all shards failed",
    "phase": "query",
    "grouped": true,
    "failed_shards": [
      {
        "shard": 0,
        "index": "suggest",
        "node": "QD4HN-gKRg-Zt_jRPNRjIw",
        "reason": {
          "type": "null_pointer_exception",
          "reason": null
        }
      }
    ],
    "caused_by": {
      "type": "null_pointer_exception",
      "reason": null,
      "caused_by": {
        "type": "null_pointer_exception",
        "reason": null
      }
    }
  },
  "status": 500
}