preg_replace_callback errors

[proxy_fcgi:error] [pid 2743] Got error ‘PHP message: PHP Warning: preg_replace_callback(): Requires argument 2, ‘<a rel="nofollow"\\1′, to be a valid callback in /home/username/public_html/wp-content/plugins/wpa-seo-auto-linker/wpa-seo-auto-linker-functions.php on line 36\n’

showing in error log. plugin works fine, but this is filling up logfiles. ideas?