use nullptr in Hybrid.h (#29)
use nullptr in Hybrid.h (#29)

Summary:
## Motivation

Why are you making this change?

What did you change?

How does the code work?

Why did you choose this approach?
Pull Request resolved: https://github.com/facebookincubator/fbjni/pull/29

Test Plan:
How did you test this change?
Any change that adds functionality should add a unit test as well.

Reviewed By: mhorowitz

Differential Revision: D19347378

Pulled By: passy

fbshipit-source-id: 4022289d222e507d82ce601239719b899e40867c

facebookincubator/fbjni,facebookincubator/fbjni,facebookincubator/fbjni,facebookincubator/fbjni