Summary:
If a negative height/width comes down, cap it to `0.0`.
Issue fixed: #566
Also fixes t16455632 internally.
- [x] All tests pass. Demo project builds and runs.
- [x] I added tests, an experiment, or detailed why my change isn't tested.
- [x] I added an entry to the `CHANGELOG.md` for any breaking changes, enhancements, or bug fixes.
Closes https://github.com/Instagram/IGListKit/pull/583
Differential Revision: D4797520
Pulled By: jessesquires
fbshipit-source-id: 3eeec5244a445bb451460286b4f006ca0d9c67d1