Error removing plugin

I receive an error while trying to remove the Anspress plugin:

Fatal error: Uncaught Error: Call to undefined function ap_opt() in ../public_html/wp-content/plugins/anspress-question-answer/anspress-question-answer.php:491 Stack trace: #0 ../public_html/wp-includes/plugin.php(525): AnsPress_Init::anspress_uninstall(”) #1 ../public_html/wp-admin/includes/plugin.php(1031): do_action(‘uninstall_anspr…’) #2 /../public_html/wp-admin/includes/plugin.php(829): uninstall_plugin(‘anspress-questi…’) #3 ../public_html/wp-admin/plugins.php(346): delete_plugins(Array) #4 {main} thrown in ../public_html/wp-content/plugins/anspress-question-answer/anspress-question-answer.php on line 491