App crashes when fetching more messages

[0x-r4bbit]

This is something that first came up during testing the community history archive protocol, which is why I thought the crash is related to those changes. However it turns out this crash is reproducable when there's not community history archive in play at all.

Here's how it happens:

1. Create a community
2. Create a channel
3. Send some messages to that channel (although, possible this isn't necessary)
4. Invite someone to that community
5. Login as that someone, join the community
6. Enter the channel, and click "Fetch more messages"

The app crashes with:

Traceback (most recent call last)
/home/rabbit/projects/status-im/status-desktop/src/nim_status_client.nim(164) nim_status_client
/home/rabbit/projects/status-im/status-desktop/src/nim_status_client.nim(161) mainProc
/home/rabbit/projects/status-im/status-desktop/vendor/nimqml/src/nimqml/private/qguiapplication.nim(29) exec
/home/rabbit/projects/status-im/status-desktop/vendor/nimqml/src/nimqml/private/qobject.nim(49) qobjectCallback
/home/rabbit/projects/status-im/status-desktop/vendor/nimqml/src/nimqml/private/qobject.nim(34) onSlotCalled
/home/rabbit/projects/status-im/status-desktop/vendor/nimbus-build-system/vendor/Nim/lib/core/macros.nim(587) onSlotCalled
/home/rabbit/projects/status-im/status-desktop/src/app/modules/main/chat_section/chat_content/messages/view.nim(152) requestMoreMessages
/home/rabbit/projects/status-im/status-desktop/src/app/modules/main/chat_section/chat_content/messages/io_interface.nim(112) requestMoreMessages
/home/rabbit/projects/status-im/status-desktop/src/app/modules/main/chat_section/chat_content/messages/module.nim(474) requestMoreMessages
/home/rabbit/projects/status-im/status-desktop/src/app/modules/main/chat_section/chat_content/messages/controller.nim(245) requestMoreMessages
/home/rabbit/projects/status-im/status-desktop/src/app_service/service/mailservers/service.nim(83) requestMoreMessages
SIGSEGV: Illegal storage access. (Attempt to read from nil?)
make: *** [Makefile:582: run-linux] Segmentation fault (core dumped)

Notice how the stack trace says that it fails at requestMoreMessages.
This calls SyncChatFromSyncedFrom in status-go.
I tried debugging this but it's kinda hard. The moment the fetch more button is clicked the app crashes even ignoring logs.

One important note:
When restarting the app (as that invited someone) and entering the channel again, hitting the "fetch more messages" button now doesn't crash it anymore.
So this seems to be only an issue upon recent community invite...

[0x-r4bbit]

Happy to investigate this further, but will work on landing status-im/status-go#2576 and status-im/status-go#2585

[0x-r4bbit]

Noticed that the exact same thing happens after importing a community (and then trying to fetch more messages)