I suspect this happened after a group was deleted from Telegram.
May 26 00:22:32 debian slidge[72962]: File "/usr/lib/slidge/lib/python3.11/site-packages/slidge/plugins/telegram/group.py", line 56, in by_group_id
May 26 00:22:32 debian slidge[72962]: return await self.by_legacy_id(self.group_ids[group_id])
May 26 00:22:32 debian slidge[72962]: ~~~~~~~~~~~~~~^^^^^^^^^^
May 26 00:22:32 debian slidge[72962]: KeyError: 0000000000
If this didn't crash the gateway but just pollutes the log, then it's been fixed by https://git.sr.ht/~nicoco/slidgram/commit/46214761332192931db6123f99897333ce78ee2a
Unfortunately the debian nightlies build have been broken since before that commit, so you didn't get it yet…
Please re-open if I'm mistaken and this actually does something worse than logging an error.