Address schema parsing bug for `array` type if `items` is null or missing & handle custom response code

Addresses Issue: #28 (closed)

• Address schema parsing bug for array type if items is null or missing. Indexer fails instead of skipping over the attribute.

Here is example of such attribute:

"Wellbores": {
  "pattern": ".*U1A1NjA3MDM2Mzk5MzUy:.*",
  "description": "The Well ID reference.",
  "type": "array"
}

• Handle custom response code, as Indexer has few. Indexer throws exceptions otherwise.