Unclear error message

Hi,

I'm using http://jsfiddle.net/kartagis/z72nvLz7/ to create a file on my server. However I'm getting Missing data the file upload can not be completed. Looking at the code below, I am fairly certain that neither $file nor $filename are empty (please see the below screenshot). So, what am I doing wrong?

The code:

if (!isset($file['file']) || empty($file['filename'])) {
  return services_error(t("Missing data the file upload can not be completed"), 500);
}