don't remove top hidden elements in the tree

lib/single-file/doc-helper.js

@@ -177,11 +177,11 @@ this.docHelper = this.docHelper || (() => {
 
 	function markHiddenElements(win, element, styles, markerRemovedContent) {
 		const elements = Array.from(element.childNodes).filter(node => node.nodeType == win.Node.ELEMENT_NODE);
-		elements.forEach(element => markHiddenElements(win, element, markerRemovedContent));
-		if (element.parentElement.getAttribute(markerRemovedContent) != "") {
+		if (element.getAttribute(markerRemovedContent) == "") {
 			element.removeAttribute(markerRemovedContent);
 		} else {
 			styles.delete(element);
+			elements.forEach(element => markHiddenElements(win, element, styles, markerRemovedContent));
 		}
 	}