Content-length header is missing when xsendfile() is enabled

enable xsendfile in web server and in config.php load dashboard page check (as explained here : http://superuser.com/a/295363 ) if there is Content-length header in http response for static contents served by theme/jquery.php or theme/image.php scripts (ex: png user picture). note : if browser client handle gzip contents, svg contents served by theme/image.php will not have Content-length header in their response if browser client handle gzip contents, css and javascript contents served by theme/jquery.php will not have Content-length header in their response