Minor GetValueOrNullTest cleanup
Minor GetValueOrNullTest cleanup

Reviewed By: thedavekwon

Differential Revision: D39413014

fbshipit-source-id: 20242cbe308e511c8d9026390b817e677357aa4c

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift