Clearing out a custom field values still reports as NOT EMPTY in JQL search

Issue Summary

For a multi line custom field using the Wiki Style Renderer, clear out the values for the field value.

Search for the field in JQL within your project as 

customFieldName is not EMPTY AND project=YourProjectName

This would still return the issues where the customFieldName has no value present.

Steps to Reproduce

1. Create a multi line text custom field. And use the wiki Style Renderer for this.
2. Input some value in this multi line text custom field within your issue.
3. Delete the value for the custom field.
4. Search in JQL, with the following query:

   1. customFieldName is not EMPTY AND project=YourProjectName

1. It would return the above issue as well, where you just cleared out the value ( the one in step 3).

Expected Results

The issue where the custom field value was deleted should not be listed.

Actual Results

The issue where the custom field value was deleted is still getting listed.

In the HAR file, when clearing out the value from the custom field (customfield_10031) using the Wiki style renderer, the request contains the following:

{
  "fields": {
    "customfield_10031": {
      "type": "doc",
      "version": 1,
      "content": [
        {
          "type": "paragraph",
          "content": []
        }
      ]
    }
  }
}

Comparing this to the HAR file inputs for a custom field using the default text renderer, the request is:

 {
  "fields": {
    "customfield_10031": ""
  }
}

Workaround

You can use the Default Text renderer instead of the WikiStyle Renderer and the search functionality works as expected.