Backend Payment Plugin User Points

-- HikaShop version -- : 4.2.2
-- HikaSerial version -- : 3.0.1
-- Joomla version -- : 3.9.11
-- PHP version -- : 7.2
-- Browser(s) name and version -- : FireFox 69.0.3
-- Error-message(debug-mod must be tuned on) -- : 0 Call to a member function display() on null
/home/hops/public_html/plugins/hikashoppayment/userpoints/userpoints_configuration.php:39

System -> Payment Methods -> New -> Hikashop UserPoints Payment Plugin results in error message: 0 Call to a member function display() on null

1 () JROOT/plugins/hikashoppayment/userpoints/userpoints_configuration.php:39

Please help.

FYI - from a different post regarding the frontend I did add the code below before line 39 and it did not resolve the issue.

$this->categoryType = hikashop_get('type.categorysub');
$this->categoryType->type = 'tax';
$this->categoryType->field = 'category_id';