deserializeResource fails when blacklistOnDeserialize is set but no attributes are present

[pichfl]

When deserializing a patch request for relationships you may encounter a payload that does not include any attributes, see https://jsonapi.org/format/#crud-updating-resource-relationships

This means that this code will fail:

json-api-serializer/lib/JSONAPISerializer.js

Lines 473 to 476 in ae86169

	// Remove unwanted keys (blacklistOnDeserialize option)
	if (resourceOpts.blacklistOnDeserialize.length > 0) {
	data.attributes = _pick(data.attributes, _difference(Object.keys(data.attributes), resourceOpts.blacklistOnDeserialize));
	}