Detector Rail Power Bug

I was setting up a detector rail for my minecart track and placed redstone under it and it was powered automatically. It stays powered when the track is removed.

What I expected to happen was...:
The redstone to be unpowered as it was not powered by any other source.

What actually happened was...:
The redstone was powered from no source.

Steps to Reproduce:
1. Place a Detector Rail on a block
2. Place redstone below the block the powered rail is on
3. Redstone is also still powered when the detector rail is removed

The screenshots were taken in creative for clarity.