A TimThumb error has occured

The following error(s) occured:

The remote file is not a valid image. Mimetype = ''/var/www/vhosts/ihredomain.de/httpdocs/wordpress/gladrags.de/wp-content/plugins/justified-image-grid/cache/timthumb1Jj9uK

Query String : src=http%3A%2F%2Fwww.gladrags.de%2Fwp-content%2Fgallery%2Ffilm-und-fernsehen%2Ffilm_und_fernsehen_kostuem_012.jpg&h=603&w=451&q=35&f=.jpg
TimThumb version : JIG