[Centaury] Restore BROWSER_NEW_TAB_URL check.

application/basilisk/base/content/utilityOverlay.js

@@ -37,7 +37,7 @@ var gBidiUI = false;
  * Determines whether the given url is considered a special URL for new tabs.
  */
 function isBlankPageURL(aURL) {
-  return aURL == "about:blank" || aURL == "about:newtab" || aURL == "about:logopage";
+  return aURL == "about:blank" || aURL == BROWSER_NEW_TAB_URL || aURL == "about:logopage";
 }
 
 function getBrowserURL()