It's normal.... Pg110 of the manual
In cold or damp weather conditions, the headlights, tail lights and turn signals may mist up inside temporarily. This is normal and in no way effects the useful life of the vehicle lighting system.
Just been to the dealer, to start of with the it's normal to get condensation etc. Then mentioned the small crack on the inside, so damage not covered by the warranty. So mentioned the bulleting about the problem and they then looked it up and seemed genuinely surprised when they found it. Looking at the bulleting mine was in the early stages of the cracking. So booked in for Thursday to have it replaced, and to be fair to the dealer they were good with the way they dealt with me.