mob eggs don't spawn mobs at all

Mobs aren't spawning from eggs

What I expected to happen was...:
A mob would spawn and drop down

What actually happened was...:
It didn't spawn at all (I tryed ocelots and pigs, this happened, it was peaceful mode.)

Steps to Reproduce:
1. Put diffuculty on peaceful
2. Get a mob egg
3. try to spawn a mob