Can’t activate plugin, fatal error

I am unable to activate the WP User Manager plugin, because it says activating the plugin will give a fatal error. Below you can see what the error log says. I would really appreciate it helping me out out here..

2025-06-19T16:47:23+00:00 CRITICAL Uncaught TypeError: array_merge(): Argument #2 must be of type array, false given in /var/www/vhosts/mywebsite.nl/httpdocs/wp-content/plugins/wp-user-manager/includes/install.php:197 CONTEXT: {“error”:{“type”:1,”file”:”/var/www/vhosts/mywebsite.nl/httpdocs/wp-content/plugins/wp-user-manager/includes/install.php”,”line”:197},”remote-logging”:true,”backtrace”:[“”,”#0 /var/www/vhosts/mywebsite.nl/httpdocs/wp-content/plugins/wp-user-manager/includes/install.php(197): array_merge(Array, false)”,”#1 /var/www/vhosts/mywebsite.nl/httpdocs/wp-content/plugins/wp-user-manager/includes/install.php(263): wpum_install_emails()”,”#2 /var/www/vhosts/mywebsite.nl/httpdocs/wp-content/plugins/wp-user-manager/includes/install.php(35): wpum_run_install()”,”#3 /var/www/vhosts/mywebsite.nl/httpdocs/wp-includes/class-wp-hook.php(324): wp_user_manager_install(false)”,”#4 /var/www/vhosts/mywebsite.nl/httpdocs/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(NULL, Array)”,”#5 /var/www/vhosts/mywebsite.nl/httpdocs/wp-includes/plugin.php(517): WP_Hook->do_action(Array)”,”#6 /var/www/vhosts/mywebsite.nl/httpdocs/wp-admin/includes/plugin.php(703): do_action(‘activate_wp-use…’, false)”,”#7 /var/www/vhosts/mywebsite.nl/httpdocs/wp-admin/plugins.php(60): activate_plugin(‘wp-user-manager…’, ‘https://mywebs…’, false)”,”#8 {main}”,”thrown”]}