API hangs when an empty array is inserted into a reference field

[fra967]

Consider this collection

{
  "fields": {
    "name": {
      "type": "String",
      "label": "Name",
      "required": false
    },
    "images": {
      "type": "Reference",
      "label": "Image",
      "required": false,
      "settings": {
        "collection": "media",
        "multiple": true,
        "fields": [
          "image",
          "altText",
          "caption",
          "credits"
        ]
      }
    }
  },
  "settings": {
    "authenticate": true,
    "count": 20
  }
}

and the following insert requests:

{"name":"My name","images":""}
works fine, an empty string is inserted

{"name":"My name","images":[""]}
works fine, an array with an empty string is inserted

{"name":"My name","images":[]}
hangs indefinitely: i would expect an empty array to be inserted (or nothing), and a response to be returned

API 2.1.1