I found the bug myself !
Replace
if($show_game)
{ $q="SELECT a.title,a.price, a.priceunit,a.imageURL as src, a.id, a.game_id, b.hits,mcat.catid FROM #__medialibrary_game AS a, #__medialibrary AS b
nLEFT JOIN #__medialibrary_categories AS mcat ON mcat.mediaid=b.id " .
by
if($show_game)
{ $q="SELECT a.title,a.price, a.priceunit,a.imageURL as src, b.id, a.game_id, b.hits,mcat.catid FROM #__medialibrary_game AS a, #__medialibrary AS b
nLEFT JOIN #__medialibrary_categories AS mcat ON mcat.mediaid=b.id " .
Gerald