Unable to load category checkbox tree

[jwcarder]

Preconditions

1. Magento 2.2.4 without sample data is installed
2. Multiple root categories are added (3)
3. Multiple subcategories added to each root category (2 each)

Steps to reproduce

1. In Admin, navigate to Marketing-Catalog Price Rule
2. Add a new rule
3. Under conditions, add a condition and select Category
4. Click on the ... link
5. Click the open chooser button

Expected result

1. Category checkbox tree loads

Actual result

1. Category checkbox tree fails to load and script enters an endless loop

After some digging, it appears as though the issue may be in the following file -vendor/magento/module-catalog/view/adminhtml/web/js/category-checkbox-tree.js line 164

categoryLoader.buildCategoryTree = function (parent, config) {// eslint-disable-line no-shadow

                if (!config) {
                    return null;
                }

                if (parent && config && config.length) {
                    for (i = 0; i < config.length; i++) {
                        categoryLoader.processCategoryTree(parent, config, i);
                    }
                }
            };

The counter in the for loop will get a config.length equal to the number of root categories, but will not increment past the number of subcategories contained in the root category.

[hostep]

Hi @jwcarder

I'm going to close this issue as it duplicates #15121, which already got fixed in #15265 (d9dc66c) and the fix should get included in Magento 2.2.5