fix undefined value

lib/single-file/processors/hooks/content/content-hooks-frames.js

@@ -134,6 +134,7 @@ function injectedScript() {
 	if (typeof globalThis == "undefined") {
 		window.globalThis = window;
 	}
+	const document = globalThis.document;
 	const console = globalThis.console;
 	const dispatchEvent = event => globalThis.dispatchEvent(event);
 	const CustomEvent = globalThis.CustomEvent;