IP address field is empty bug

I'm using this plugin, and I'm getting the exception when this field is empty (null). One checking line on the beginning solved this problem for me.

sorting/ip-address.js

@@ -18,6 +18,7 @@
 
 jQuery.extend( jQuery.fn.dataTableExt.oSort, {
 	"ip-address-pre": function ( a ) {
+		if (a == null) { return 0 }
 		var i, item;
 		var m = a.split("."),
 			n = a.split(":"),
@@ -100,4 +101,4 @@ jQuery.extend( jQuery.fn.dataTableExt.oSort, {
 	"ip-address-desc": function ( a, b ) {
 		return ((a < b) ? 1 : ((a > b) ? -1 : 0));
 	}
-});
+});