The fact that this callback depends on sendPushNotifs makes it so the notifs processing still uses an outdated store.

If necessary, we can use a "step-based approach" where we wait for the appropriate data to appear in Redux that would make us confident that sendPushNotifs is up-to-date. This sort of approach is complicated to get right, but we use it in login-hooks.js and registration-server-call.js, and previously used it in relationship-hooks.js before D13496 (see D13443 for original approach). If we take this approach, we should make sure to implement a timeout so that if the data never appears in Redux, we still eventually reject the returned promise

Actually, this works correctly, and the fact that sendPushNotifs throws doesn't indicate that our solution is incorrect. When we leave a chat, it is expected that after processing the operation, the thread and its members aren't present in the store.

The issue here is quite different: when we reach this code, we should somehow know to whom we should send the notifs. It might be too late to read this from the store, so we should find an alternative way of passing this information.

This might be a bit complicated because when we add a new member to a thread, we should use the state from after the processing. And when we leave a thread, we should use the state from before.