Quitting the game while curing villagers causes them to forget curing history

Normally, a villager being cured multiple times can offer a heavier trading discount than one being cured once. However, when one save & quit the game while a villager is still being cured, upon returning to the game the villager will forget whether it has been cured before.

Steps to Reproduce:

1. Convert and cure a villager (A) multiple times, and record the trading prices. The prices would drop every time A is cured again.
2. Convert and cure A again, but save and quit the game when A is still in zombie form.
3. Return to the game. A should now be a villager.
4. Check the trading price of A. The price would be as if A is cured the first time, regardless of how many cures have been performed in step 1.