How to Fallback to a complete transparent or no render for a Unity5 Transparent glass custom shader?

My glass shader is using a custom Unity5 script. It is used to render the window of cars and aeroplanes. Since is a first person game, I wish to look out the vehicle also when the glass shader is not working well. I need a "Fallback" that do not render or renders transparency. But if I put: Fallback "Transparent/VertexLit" or Fallback "Transparent", then renders the pure white colour.

How to Fallback completely to a transparent shader that works in all device or that it do not render at all?