Plugin could not be activated because it triggered a fatal error

Fatal error: Uncaught Error: Class 'WPUM_Extension_Activation' not found in /home/divzero3/public_html/Warriors.gg/wp-content/plugins/wpum-username-length/wpum-username-length.php:187 Stack trace: #0 /home/divzero3/public_html/Warriors.gg/wp-content/plugins/wpum-username-length/wpum-username-length.php(79): WPUM_Username_Length->addon_can_run() #1 /home/divzero3/public_html/Warriors.gg/wp-content/plugins/wpum-username-length/wpum-username-length.php(65): WPUM_Username_Length->__construct() #2 /home/divzero3/public_html/Warriors.gg/wp-content/plugins/wpum-username-length/wpum-username-length.php(209): WPUM_Username_Length::instance() #3 /home/divzero3/public_html/Warriors.gg/wp-content/plugins/wpum-username-length/wpum-username-length.php(212): WPUMUL() #4 /home/divzero3/public_html/Warriors.gg/wp-admin/includes/plugin.php(2141): include('/home/divzero3/...') #5 /home/divzero3/public_html/Warriors.gg/wp-admin/plugins.php(175): plugin_sandbox_scrape('wpum-username-l...') #6 {main} thrown in /home/divzero3/public_html/Warriors.gg/wp-content/plugins/wpum-username-length/wpum-username-length.php on line 187