Fix issues reported by Sentry

[S7evinK]

This should fix a few issues reported by Sentry, e.g. HTTP500 when trying to update room keys which don't exist.

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (c08c740) 65.24% compared to head (c8baa39) 65.24%.

❗ Current head c8baa39 differs from pull request most recent head 53df425. Consider uploading reports for the commit 53df425 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3143   +/-   ##
=======================================
  Coverage   65.24%   65.24%           
=======================================
  Files         504      504           
  Lines       56218    56218           
=======================================
  Hits        36680    36680           
- Misses      15717    15719    +2     
+ Partials     3821     3819    -2     

Flag	Coverage Δ
unittests	49.75% <0.00%> (-0.04%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
syncapi/streams/stream_pdu.go	66.89% <0.00%> (-1.04%)	⬇️
userapi/internal/user_api.go	64.93% <0.00%> (ø)

... and 11 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.