delete timeout property

lib/lazy/web-lazy-loader-after.js

@@ -30,7 +30,7 @@
 	}
 	if (window._singleFile_timeoutScroll) {
 		clearTimeout(window._singleFile_timeoutScroll);
-		window._singleFile_timeoutScroll = null;
+		delete window._singleFile_timeoutScroll;
 		delete document.documentElement.scrollTop;
 		window.scrollY = window.pageYOffset = window._singleFile_offsetY;
 		dispatchEvent(new UIEvent("scroll"));