Uncaught TypeError: sizeof(): Argument #1

A site I maintain for a client that uses fusionSpan | netFORUM Single Sign OnVersion 1.3.3 has experienced the following error:

Error Details
=============
An error of type E_ERROR was caused in line 65 of the file /nas/content/live/XXXXXXX/wp-content/plugins/avectra-netforum-single-sign-on/src/WP/Views/View.php. Error message: Uncaught TypeError: sizeof(): Argument #1 ($value) must be of type Countable|array, null given in /nas/content/live/XXXXXXX/wp-content/plugins/avectra-netforum-single-sign-on/src/WP/Views/View.php:65
Stack trace:
#0 /nas/content/live/XXXXXXX/wp-content/plugins/avectra-netforum-single-sign-on/src/WP/Views/View.php(65): sizeof(NULL)
#1 /nas/content/live/XXXXXXX/wp-content/plugins/avectra-netforum-single-sign-on/src/WP/Views/View.php(37): WP\Views\View->makeField('wsdl', Array)
#2 [internal function]: WP\Views\View->WP\Views\{closure}(Array, 'wsdl')
#3 /nas/content/live/XXXXXXX/wp-content/plugins/avectra-netforum-single-sign-on/src/WP/Views/View.php(34): array_walk(Array, Object(Closure))
#4 [internal function]: WP\Views\View->WP\Views\{closure}(Array, 'single sign on')
#5 /nas/content/live/XXXXXXX/wp-content/plugins/avectra-netforum-single-sign-on/src/WP/Views/View.php(28): array_walk(Array, Object(Closure))
#6 /nas/content/live/XXXXXXX/wp-content/plugins/avectra-netforum-single-sign-on/src/WP/Views/View.php(20): WP\Views\View->init()
#7 /nas/content/live/XXXXXXX/wp-content/plugins/avectra-netforum-single-sign-on/src/Netforum/Traits/SingletonTrait.php(19): WP\Views\View->__construct()
#8 /nas/content/live/XXXXXXX/wp-includes/class-wp-hook.php(324): WP\Views\View::getInstance('')
#9 /nas/content/live/XXXXXXX/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters('', Array)
#10 /nas/content/live/XXXXXXX/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#11 /nas/content/live/XXXXXXX/wp-content/plugins/avectra-netforum-single-sign-on/assets/templates/main.tpl(11): do_action('nf_body')
#12 /nas/content/live/XXXXXXX/wp-content/plugins/avectra-netforum-single-sign-on/src/WP/Views/Page.php(29): include_once('/nas/content/li...')
#13 /nas/content/live/XXXXXXX/wp-includes/class-wp-hook.php(324): WP\Views\Page::getTpl('')
#14 /nas/content/live/XXXXXXX/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters('', Array)
#15 /nas/content/live/XXXXXXX/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#16 /nas/content/live/XXXXXXX/wp-admin/admin.php(259): do_action('toplevel_page_n...')
#17 {main}
? thrown

How do we fix the error?

WordPress: Version 6.6.2
Theme: Twenty Twenty-Four version 1.2
Hosted on WPEngine (could be related to www.ads-software.com actions against WPEngine).
PHP: Version 8.2.24