Warning: Trying to access array offset on value of type bool in Drupal\abtestui\Form\ABTestForm->buildForm() (line 195

Problem/Motivation

After installing the module I am getting the following error when visiting /admin/config/user-interface/ab_test/add

Warning: Trying to access array offset on value of type bool in Drupal\abtestui\Form\ABTestForm->buildForm() (line 195 of modules/contrib/abtestui/src/Form/ABTestForm.php).
Drupal\abtestui\Form\ABTestForm->buildForm(Array, Object, NULL)
call_user_func_array(Array, Array) (Line: 531)

Steps to reproduce

1. install module
2. go to /admin/config/user-interface/ab_test/add
3. Error message should be displayed

Proposed resolution

Looks like the form value needs to be checked if it is empty.

Remaining tasks

1. Submit patch/PR

User interface changes

None

API changes

None

Data model changes

None