fixes #881 - or should. blanks out the iframe so that any ads or othe…

…r junk loaded in the iframe are destroyed. was unable to get any imgur pages with audio ads, so couldn't 100% verify, but this should work!

lib/modules/showImages.js

@@ -181,6 +181,7 @@ modules['showImages'] = {
 					this.imageTrackFrame = document.createElement('iframe');
 					this.imageTrackFrame.addEventListener('load', function() {
 						setTimeout(modules['showImages'].imageTrackShift, 300);
+						modules['showImages'].imageTrackFrame.contentWindow.location.replace('about:blank');
 					}, false);
 					this.imageTrackFrame.style.display = 'none';
 					this.imageTrackFrame.style.width = '0px';