Adds a css class of thumbnail to local covers.
Don't show the 1px "No image found" image
(since we'll ususally try another image provider)
Signed-off-by: Hector Castro <hector.hecaxmmx@gmail.com>
Box with "No cover image availabe" fixed when syspref OPACLocalCoverImages
set to display
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>