Need help for Inmobi in Unity WP8.

I’m Hoang. I created a game in Unity and build to WP8 project. I want using Inmobi ads networks in my game.
I download Inmoi wp8 sdk and include source code to my project.
Banner is showed is okie. I click to banner it open web(or wp store) and when I press backkey to back my game it crash.

people who do not know the solution to it. please help me.