replace also empty images

lib/single-file/single-file-core.js

@@ -448,7 +448,7 @@ this.SingleFileCore = this.SingleFileCore || (() => {
 				if (this.options.lazyLoadImages) {
 					this.doc.querySelectorAll("img[data-src]").forEach(imgElement => {
 						const imgData = this.options.imageData[Number(imgElement.getAttribute(dataAttributeName))];
-						if (!imgElement.getAttribute("src") && imgElement.getAttribute("data-src")) {
+						if ((!imgElement.getAttribute("src") || imgElement.getAttribute("src") == EMPTY_IMAGE) && imgElement.getAttribute("data-src")) {
 							imgData.src = imgElement.dataset.src;
 							imgElement.setAttribute("src", imgElement.dataset.src);
 							imgElement.removeAttribute("data-src");