Game crashed when Villagers become willing

What I expected to happen was...:
Baby villagers will spawn.

What actually happened was...:
Game crashed, sending me a crash report after some villagers are willing at the same time.

Steps to Reproduce:

1. Under the effect of "Hero of the village" 
2. Give the villagers enough food. etc, bread.
3. Stay near them and wait until they are willing to mate.