avoided hiding already hidden elements

Former-commit-id: d0f5a57184bf3bebb54b7c9dc36411234c7ff14b

lib/single-file/single-file-helper.js

@@ -38,7 +38,7 @@ this.singlefile.lib.helper = this.singlefile.lib.helper || (() => {
 	const LAZY_SRC_ATTRIBUTE_NAME = "data-single-file-lazy-loaded-src";
 	const STYLESHEET_ATTRIBUTE_NAME = "data-single-file-stylesheet";
 	const SELECTED_CONTENT_ATTRIBUTE_NAME = "data-single-file-selected-content";
-	const IGNORED_REMOVED_TAG_NAMES = ["NOSCRIPT", "DISABLED-NOSCRIPT", "META", "LINK", "STYLE", "TITLE", "TEMPLATE", "SOURCE", "OBJECT", "SCRIPT"];
+	const IGNORED_REMOVED_TAG_NAMES = ["NOSCRIPT", "DISABLED-NOSCRIPT", "META", "LINK", "STYLE", "TITLE", "TEMPLATE", "SOURCE", "OBJECT", "SCRIPT", "HEAD"];
 	const REGEXP_SIMPLE_QUOTES_STRING = /^'(.*?)'$/;
 	const REGEXP_DOUBLE_QUOTES_STRING = /^"(.*?)"$/;
 	const FONT_WEIGHTS = {
@@ -282,8 +282,10 @@ this.singlefile.lib.helper = this.singlefile.lib.helper || (() => {
 			const visibility = computedStyle.getPropertyValue("visibility");
 			hidden = display == "none";
 			if (hidden) {
-				element.setAttribute(HIDDEN_CONTENT_ATTRIBUTE_NAME, "");
-				markedElements.push(element);
+				if (!IGNORED_REMOVED_TAG_NAMES.includes(element.tagName)) {
+					element.setAttribute(HIDDEN_CONTENT_ATTRIBUTE_NAME, "");
+					markedElements.push(element);
+				}
 			} else if ((opacity == "0" || visibility == "hidden") && element.getBoundingClientRect) {
 				const boundingRect = element.getBoundingClientRect();
 				hidden = !boundingRect.width && !boundingRect.height;