Fatal error: undefined function pt_unserialize_to_array()

With version 5.0.4 I get a fatal error:

PHP Fatal error:  Uncaught Error: Call to undefined function pt_unserialize_to_array() in /.../wp-content/plugins/paytium/includes/notification-functions.php:21
Stack trace:
#0 /.../wp-content/plugins/paytium/class-paytium.php(712): paytium_add_notification()
#1 /.../wp-includes/class-wp-hook.php(353): Paytium->includes()
#2 /.../wp-includes/class-wp-hook.php(377): WP_Hook->apply_filters()
#3 /.../wp-includes/plugin.php(523): WP_Hook->do_action()
#4 /.../wp-settings.php(779): do_action()
#5 /.../wp-config.php(101): require_once('...')
#6 /.../wp-load.php(50): require_once('...')
#7 /.../wp-blog-header.php(13): require_once('...')
#8 /.../index.php(17): require('...')
#9 {main}
  thrown in /.../wp-content/plugins/paytium/includes/notification-functions.php on line 21

This happens, because the function paytium_add_notification() is called while includes/payment-functions.php hasn’t been loaded yet.

As a quick fix I’ve added this at line 689 of class-paytium.php:

include_once( PT_PATH . 'includes/payment-functions.php' );

I know it’s loaded a bit further down the file, but it shouldn’t hurt because of the include_once and it’s clear the order is not correct.