Lightbox / slimbox special characters patch

[Marco Dimichele]

The slimbox version included in virtuemart does not handle properly images with special characters, like (, [ and sometimes spaces.
The bug can be solved editing the file /components/com_virtuemart/js/slimbox/js/slimbox.js,
and replacing the line 139:
this.image.style.backgroundImage = 'url('+this.images[this.activeImage][0]+')';
with:
this.image.style.backgroundImage = 'url("'+this.images[this.activeImage][0]+'")';