Error validating a categorization job with categorization_filters field

[edsavage]

If the categorization_filters field is added to the definition of a categorization job (necessarily in the the advanced editor) e.g.

{
  "job_id": "categorize_messages",
  "description": "",
  "groups": [],
  "analysis_config": {
    "bucket_span": "15m",
    "detectors": [
      {
        "function": "count",
        "by_field_name": "mlcategory"
      }
    ],
    "influencers": [
      "mlcategory"
    ],
    "per_partition_categorization": {
      "enabled": false,
      "stop_on_warn": false
    },
    "categorization_field_name": "message",
    "categorization_filters": []
  },
  "data_description": {
    "time_field": "timestamp"
  },
  "analysis_limits": {
    "model_memory_limit": "26MB"
  },
  "model_plot_config": {
    "enabled": false,
    "annotations_enabled": false
  }
}

the following error is generated

Although not part of the job creation wizards I would expect the field to be accepted as valid if present.

[elasticmachine]

Pinging @elastic/ml-ui (:ml)