Fix a possible crash.
Fix a possible crash.

Summary:
Fix a possible crash.

We saw some crashes that might have been caused by this. No repro available,
so this is not a confirmed fix.

Reviewed By: maxmg22

Differential Revision: D6263456

fbshipit-source-id: d701183ea51d9d335e5ff09d30bf4cde33bccccc

facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex