Summary:
Apparently it's possible for `!isEmpty()` to be true and `peek` to be non-null, but for `poll()` to be false. It doesn't really make sense to me, and I don't have a repro, but that's what logs are showing.
I suspect a teardown race condition or /maybe/ a Fabric/non-Fabric handoff race condition. Neither of those make a ton of sense, though.
The mitigation is fairly straightforward: we are just much more cautious with how we treat the queue and assume everything could be null.
This impacts Fabric and non-Fabric equally.
Changelog: [Internal]
Reviewed By: motiz88
Differential Revision: D22593924
fbshipit-source-id: 7748121951a64941fa6da2bd25ebf070be6dc89c
Joshua Gross
980900c634