Loads local image even when external image is set

In float-to-top-button.js line 24 (fttb_img.src = fttb.imgurl+fttb.arrow_img;) causes the local image to load even when arrow_img_url is set. This line should either be removed or replaced with: fttb_img.src = fttb.arrow_img_url == '' ? fttb.imgurl+fttb.arrow_img : fttb.arrow_img_url;

https://wordpress.org/plugins/float-to-top-button/