Prevented bypass with empty <iframe>.

Fixes #58

lib/sharedFunctions.js

@@ -35,8 +35,13 @@ function check(stack, url, blockMode){
 function checkURL(url, blockMode){
 	"use strict";
 	
-	if (url.protocol === "about:" || url.protocol === "chrome:") {
-		return "allow";
+	switch (url.protocol){
+		case "about:":
+			if (url.href === "about:blank"){
+				break;
+			}
+		case "chrome:":
+			return "allow";
 	}
 	
 	var mode = "block";