Fix issue #2470: Incorrect response when errors occurred

[atzedus]

Fix issue #2470: Incorrect response when errors occurred

Old Result:

{
  "errors": [
    {
      "message": "some error",
      "path": [
        "Kids"
      ]
    }
  ],
  "data": null
}

After PR result:

{
  "errors": [
    {
      "message": "some error",
      "path": [
        "Kids"
      ]
    }
  ],
  "data": {
       "Kids": null,
       "Martials": [1, 2, 3, 4]
  }
}

[coveralls]

Coverage decreased (-0.02%) to 75.647% when pulling 86c5659 on atzedus:issue-fix-2470 into 3008f4e on 99designs:master.