dash crack
 

Hello I have a 2001 e320 and the dash has 2 small cracks by the windshield defroster probably only a few millimeters each. You cant really notice them, but I am scared they will spread. What works best to stop them from cracking more? Is it true clear nail polish? Something special for cars? My concern is just to prevent it from spreading, not trying to hide whats there since its not noticable.
Thank You!