TypeError

Hi there, I got an automatic email from WordPress about an error generated by Noti.

This is it:

Uncaught TypeError: array_push(): Argument #1 ($array) must be of type array, null given in /home/symbol/domains/symbol.nl/public_html/wp-content/plugins/noti-activity-notification/application/Backend/Manager.php:78
Stack trace:
#0 /home/symbol/domains/symbol.nl/public_html/wp-content/plugins/noti-activity-notification/application/Backend/Manager.php(78): array_push()
#1 /home/symbol/domains/symbol.nl/public_html/wp-includes/class-wp-hook.php(324): Noti\Backend\Manager->Noti\Backend\{closure}()
#2 /home/symbol/domains/symbol.nl/public_html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters()
#3 /home/symbol/domains/symbol.nl/public_html/wp-includes/plugin.php(517): WP_Hook->do_action()
#4 /home/symbol/domains/symbol.nl/public_html/wp-admin/includes/menu.php(161): do_action()
#5 /home/symbol/domains/symbol.nl/public_html/wp-admin/menu.php(422): require_once('...')
#6 /home/symbol/domains/symbol.nl/public_html/wp-admin/admin.php(158): require('...')
#7 /home/symbol/domains/symbol.nl/public_html/wp-admin/index.php(10): require_once('...')
#8 {main}
  thrown

Can you please check this out?