Chat notifications occasionally crash app

When receiving a chat notification, sometimes pressing on it will open and instantly crash the app. Hoping that this will be easier to debug when we have Crashlytics, but documenting it here for now.

The issue names no file, test, reproduction steps, or crash trace. Start by reproducing a chat-notification tap in the TypeScript React Native app and collecting the failure details; done means the crash is identified and a verified fix is covered by an appropriate test.

索引モデルが issue の本文から書いたものです。