This is a minor bug since 0.16.0. When you tap a spawn egg on a monster spawner, it should change the spawner into whatever mob you chose, but since 0.16 it also consumes that egg and spawns a mob.
What should happen:
Tapping a monster spawner with a spawn egg should change the mob inside the spawner.
What Now Happens:
It also uses that egg to spawn one mob beside the spawner.
Steps to Reproduce:
- Place a monster spawner
- Tap it with a spawn egg
- Notice that a mob gets spawned with the egg