Failure on null has-one payloads

[sirvine]

My API generates a payload for a collection, where a single record looks like this:

    {
      "id": "16",
      "type": "contracts",
      "links": {
        "self": "/api/v1/contracts/16"
      },
      "attributes": {
        "title": "Example Title",
        "current-cycle-id": 40,
        "created-at": "2015-05-22T09:38:26.418-04:00",
        "updated-at": "2015-05-22T09:38:26.418-04:00"
      },
      "relationships": {
        "cycles": {
          "links": {
            "self": "/api/v1/contracts/16/relationships/cycles",
            "related": "/api/v1/contracts/16/cycles"
          }
        },
        "supplier": {
          "links": {
            "self": "/api/v1/contracts/16/relationships/supplier",
            "related": "/api/v1/contracts/16/supplier"
          },
          "data": null
        },
        "tower": {
          "links": {
            "self": "/api/v1/contracts/16/relationships/tower",
            "related": "/api/v1/contracts/16/tower"
          },
          "data": {
            "type": "towers",
            "id": "1"
          }
        },
        "client": {
          "links": {
            "self": "/api/v1/contracts/16/relationships/client",
            "related": "/api/v1/contracts/16/client"
          },
          "data": {
            "type": "clients",
            "id": "1"
          }
        }
      }
    }

Note that two of the has-one relationships (tower and client) include a value under the data key, but the supplier relationship is null.

The JSONAPIAdapter is chasing down all of the relationship links correctly. In the case of supplier, the resulting payload looks like:

  {
    "data": null
  }

When the JSONAPISerializer attempts to normalize this payload, it applies map to null, which causes a failure.

[sirvine]

That did the trick. Thanks!