Update IP field is empty bug

@Datatables, you are right, it should be better to use !a, then empty string case is covered as well.
And yes, I'm happy for this to be included under MIT licence.

sorting/ip-address.js

@@ -18,7 +18,7 @@
 
 jQuery.extend( jQuery.fn.dataTableExt.oSort, {
 	"ip-address-pre": function ( a ) {
-		if (a == null) { return 0 }
+		if (!a) { return 0 }
 		var i, item;
 		var m = a.split("."),
 			n = a.split(":"),