[Plugin: Ad Buttons] Use of https://

When I add image links using an https:// link, the plugin keeps pre-pending it with http:// which causes it to fail. I’ve tried to modify the code but apparently not correctly because it is still doing it. Can you tell me why this is setup this way or how to fix it?

Thank you.

http://ww.wp.xz.cn/extend/plugins/ad-buttons/