Giving some updates on this. I didn't manage to fix the bug, but after a fair amount of poking around and guesswork I have managed to recover my messages. My phone's bootloader was already unlocked, so I could boot it temporarily on a image that had root access without losing data. I installed Titanium Backup and made a backup, then uninstalled Silence 0.15.16 and installed Silence 0.16.12-unstable, and restored the backup. From there, I could open Silence without it crashing. I've now made a clear text backup and I'm currently in the process of restoring them to the Messages app with SMS Backup & Restore.
An annoying side-effect to this is that since the app crashes on startup and my device isn't rooted I can't export the message database and try to fix it, or reinstall the app without losing 6mo worth of messages.
I recently started messaging a friend on Silence. He proceeded to create a session with me, but when I clicked on the session establishment message the app crashed. Since then, I can't open the app anymore (it crashes on startup). This sounds a lot like #594 except I'm running Silence 0.15.16 (which is the latest stable on F-Droid).
I'm not entirely sure what caused it to fail initially.
Actual result: Request is accepted, app works fine Expected result: App crashes, subsequent attempts to start it make the app crash as well
I've blurred the actual homepage well enough (hopefully) to protect my contact's privacy. I'm happy to provide the unblurred version privately if you think it could help debug the issue.
Here's the stacktrace I can see in adb logcat
: https://pastebin.com/maHKGMtW