If output data has a blank string for a key the xml formatter returns nothing

Using json output works just fine, but since xml cannot contain blank name tags it seems to just crap. I am not sure what would be the preferred method to handle this. Perhaps a warning in the output, ignore blank keyed items, or replace the blank string for something else like "blank" (not proper output of course).

Either way a completely blank result seems like a bad way to handle it. If anything just print "data structure is not compatible with output format. see ...some page that explains it".

The easiest way to recreate is to use the node/retrieve action and modify the code in rest_server.views.inc as follows.

  private function render_xml($data) {
    $doc = new DOMDocument('1.0', 'utf-8');
    $root = $doc->createElement('result');
    $doc->appendChild($root);

    $data->array[''] = 'foo'; // add this
    $this->xml_recurse($doc, $root, $data);

    return $doc->saveXML();
  }

I had this happen as a field serializes it's data and ends up with a blank string as one of the keys (which is completely valid usecase).