Warning on activation

[Sun Mar 20 17:38:47.087722 2016] [:error] [pid 20818] [client 205.xxxxxxx:35872] PHP Strict Standards: call_user_func_array() expects parameter 1 to be a valid callback, non-static method SearchAutocomplete::activate() should not be called statically in /var/www/tac/wp-includes/plugin.php on line 525, referer: http://txxxx/wp-admin/update.php?action=install-plugin&plugin=search-autocomplete&_wpnonce=913882b0ea

https://ww.wp.xz.cn/plugins/search-autocomplete/