Problem with submitting "MULTI-NODE SCHEDULER" Form

I am encountering an issue After submitting "MULTI-NODE SCHEDULER" form

Steps Reproduce:

1. Installed the module using Composer with the command: composer require 'drupal/mns:^1.0'.

2: Going to /admin/config/content/mns URL and submit "MULTI-NODE SCHEDULER" form

3: After clicking the "Submit" button, it throws a warning. warning mentioned below-

Warning: Undefined array key 0 in Drupal\mns\Form\Mns_form->mns() (line 237 of modules\contrib\mns\src\Form\Mns_form.php).

I've attached an image illustrating my actions—installing the module and searching within the extended panel.