[native] Avoid crashing Redux migration if inviteLinksStore isn't initialized

Summary:
Normally we'd add a migration to initialize inviteLinksStore, but we can't add a migration before existing ones. Instead, I'll perform this migration step right before it's needed in migration 43.

Depends on D9185

Test Plan:

1. I checked out the latest codeVersion before migration 43: mobile-v1.0.238
2. I deleted the Android app from the Android emulator
3. I removed inviteLinksStore from default-state.js to simulate the effects of not having it in the store
   • To avoid this, I could have checked out an even older codeVersion, but I decided to do it this way since sometimes older codeVersions don't run anymore
4. I ran the Android app just to set up the Redux store, and then I killed it
5. I then went back to master + this diff and its parent
6. I ran the app and confirmed that the issue no longer occurs. Migration 43 succeeded, but then migration 51 crashed (tracked in ENG-4930)

Reviewers: tomek, michal

Reviewed By: tomek

Differential Revision: https://phab.comm.dev/D9186