V8: Fix JS error when using the hide search function in treepicker (#6931)

* Fix JS error when using the hide search function in treepicker

* updates with same defensive change from original pr - only explores child.children after confirming the child indeed has children

Co-authored-by: Nathan Woulfe <nathan@nathanw.com.au>

src/Umbraco.Web.UI.Client/src/views/common/infiniteeditors/treepicker/treepicker.controller.js

@@ -574,6 +574,8 @@ angular.module("umbraco").controller("Umbraco.Editors.TreePickerController",
                             var listViewResults = vm.searchInfo.selectedSearchResults.filter(i => i.parentId === child.id);
 
                             listViewResults.forEach(item => {
+                                if (!child.children) return;
+
                                 var childExists = child.children.find(c => c.id === item.id);
 
                                 if (!childExists) {