Spawners don't stop spawning monsters when covered in torches, they also spawn monsters in the ground.

Put the summary of the bug you're having here
Spawners don't stop spawning monsters when covered in torches, they also spawn monsters in the ground.
What I expected to happen was...:
Describe what you thought should happen here
The spawner to stop spawning mobs after light source was added
What actually happened was...:
Describe what happened here
It continuously spawned mobs, in walls and ground as well.
Steps to Reproduce:
1. Find Spawner
2. Add Light Source
3. Wait for Spawner