[BUGFIX] Fix warnings in the endless scroll script

Resources/Public/Scripts/ScrollBrowser.js

 /***************************************************************
  *  Copyright notice
  *
- *  (c) sgalinski Internet Services (http://www.sgalinski.de)
+ *  (c) sgalinski Internet Services (https://www.sgalinski.de)
  *
  *  All rights reserved
  *
@@ -45,12 +45,12 @@ SG.ElementScrollBrowser.prototype = {
 	resultList: null,
 
 	/**
-	 * @var string
+	 * @var string|null
 	 */
 	url: null,
 
 	/**
-	 * @var string
+	 * @var string|null
 	 */
 	lastUrl: null,
 
@@ -75,7 +75,9 @@ SG.ElementScrollBrowser.prototype = {
 		this.url = $('.tx-pagebrowse-next a').attr('href');
 		$(window).on(
 			'scroll', function() {
-				if (this.lock || !this.checkPosition() || this.url === undefined || this.url === this.lastUrl) {
+				var recordLockedOrNotInPosition = this.lock || !this.checkPosition();
+				var urlIsInvalid = typeof this.url === 'undefined' || this.url === this.lastUrl;
+				if (recordLockedOrNotInPosition || urlIsInvalid) {
 					return;
 				}