I have a temporary fix (until the plugin authors provide official updated version):
At line 125 in popup-builder/com/classes/NotificationCenter.php insert this line
if (is_array($removedNotifications))
just before the for loop:
foreach ($removedNotifications as $removedNotificationId) {
foreach ($activeNotifications as $key => $activeNotification) {
if ($activeNotification['id'] == $removedNotificationId) {
unset($activeNotifications[$key]);
}
}
}
