[Plugin: WordPress Firewall 2] Error setting whitelisted IPs

Error setting whitelist IPs:

Warning: unserialize() expects parameter 1 to be string, array given in /public_html/blog/wp-content/plugins/wordpress-firewall.php on line 625

Warning: array_unique() [function.array-unique]: The argument should be an array in /public_html/blog/wp-content/plugins/wordpress-firewall.php on line 625

Warning: Invalid argument supplied for foreach() in /public_html/blog/wp-content/plugins/wordpress-firewall.php on line 626

Any idea how to fix this?

https://www.ads-software.com/extend/plugins/wordpress-firewall-2/