[BUGFIX] Avoid global jQuery usage in RTE link wizard

The global variable $ (window.$) has been removed with #97243.
This caused the RTE link wizard to fail with a JavaScript
error as $.isEmptyObject is used in typo3link.js.

Resolves: #97301
Related: #97243
Releases: main
Change-Id: Iaafb02fa52039f8443289c4b16123e67c25b39ce
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74178


Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>

typo3/sysext/rte_ckeditor/Resources/Public/JavaScript/Plugins/typo3link.js

@@ -45,6 +45,13 @@
     }
   });
 
+  /*
+   * @param {Object} obj
+   */
+  function isEmptyObject(obj) {
+    return obj && Object.keys(obj).length === 0 && Object.getPrototypeOf(obj) === Object.prototype;
+  }
+
   /**
    * Open link browser
    *
@@ -54,7 +61,7 @@
   function openLinkBrowser(editor, element) {
     var additionalParameters = '';
 
-    if ($.isEmptyObject(element)) {
+    if (!element || isEmptyObject(element)) {
       element = CKEDITOR.plugins.link.getSelectedLink(editor);
     }
     if (element) {