When you send your old passport to get renewed, they will attach both of them the new and the old. When you get them back just go to the immigration and they will cancel both, the old passport and old visa and issue you a new visa with the same details of the old one.

Don't worry about it, should take nothing more than 5 minutes to print the new visa and stick it on the new passport.

Looks like I was late in posting this, I was in Sealine and come before a while .. :)