When pushing or pulling sloped rails without a support block adjacent to them, they disappear. This can be used with detector rails to cause redstone to be in an incorrect orientation (see attached images)

What I expected to happen was...:
The rail to drop in item form if it was pushed on top of air or the rail to become a flat rail if it was pushed on top of a block

What actually happened was...:
The rail disappeared

Steps to Reproduce:
1. create a sloped rail
2. push it into a location with no support for it using pistons
3. it disappears