declare var to fix scope error

By not declaring var i = 0, the code is referencing the i declared in the outer function. This causes an infinite loop condition that crashes browsers as multiple methods modify the value of i.

Author: keithbentrup

app/code/Magento/Catalog/view/adminhtml/web/js/category-checkbox-tree.js

@@ -168,7 +168,7 @@ define([
                 }
 
                 if (parent && config && config.length) {
-                    for (i = 0; i < config.length; i++) {
+                    for (var i = 0; i < config.length; i++) {
                         categoryLoader.processCategoryTree(parent, config, i);
                     }
                 }
@@ -185,7 +185,7 @@ define([
                 if ((node.childNodes.length > 0) || (node.loaded === false && node.loading === false)) {
                     hash.children = [];
 
-                    for (i = 0, len = node.childNodes.length; i < len; i++) {
+                    for (var i = 0, len = node.childNodes.length; i < len; i++) {
                         /* eslint-disable */
                         if (!hash.children) {
                             hash.children = [];