thanks for your replies.
i thought maybe the isolated wire will behave different and maybe could be burn and make a fire.
i,really,don't care if the wire won't take the short circuit current(if will happen,at all) and will be cut into two pieces.i,always,can solder new wire.the,only,thing that i was concern is the safety issue.i,simply,don't want that the wire will burn and make fire in the box or worse.
but if you say that the only thing that can happen is that the isolated wire will be cut like the track did,without any risk of fire,i can be more peacful.
i am sorry that it seems like i make simple things complicated but when it's belong to safety i try to be sure that everything is fine,and i happy that this site is exist and there is someone to consult with.