Custom Magento 2 module - categories widget with images - category is selected but not applied. How to fix?

Question

PHP

I was looking for a widget implementation for Magento 2 - so that you can select a category and display its children with pictures and names.
On stackexchange I found this solution
Installed, now I see a new widget in the M2 admin panel. There is a category tree, I select a category, I click on the green check mark - like the apply button - and nothing, the field remains blank.
Who is strong in php, look plz, it seems to me that something is missing, if I understand correctly, this very moment - category selection - is implemented in the file CatewithimgWidget/Block/Adminhtml/Chooser.php
ps. In the topic on stackexchange, there are errors in the files, in general, they are not critical - if necessary, I can post the corrected files, well, the code in the sense ...