minor fix

lib/frame-tree/content/frame-tree.js

@@ -258,7 +258,7 @@ this.FrameTree = this.FrameTree || (() => {
 
 	function postProcessDoc(doc) {
 		doc.head.querySelectorAll("disabled-noscript").forEach(element => {
-			const noscriptElement = this.options.doc.createElement("noscript");
+			const noscriptElement = doc.createElement("noscript");
 			Array.from(element.childNodes).forEach(node => noscriptElement.appendChild(node));
 			element.parentElement.replaceChild(noscriptElement, element);
 		});