check if colorbox is enabled first

when you first enable colorbox it should check whether the library is found or it will break js currently on website.

Drupal.behaviors.colorbox = function (context) {
     $('.colorbox').colorbox();
};

to

if (typeof colorbox == 'function' and colorbox != undefined) {
	Drupal.behaviors.colorbox = function (context) {
			$('.colorbox').colorbox();
	};
}