Don't panic if we try to dehydrate an Account libolm has created

[poljar]

Some leftover stuff from #199. Review commit by commit should be the easiest.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 76.92308% with 3 lines in your changes missing coverage. Please review.

Project coverage is 90.35%. Comparing base (3d655ad) to head (e8faeca).

Files with missing lines	Patch %	Lines
src/olm/account/mod.rs	76.92%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #204      +/-   ##
==========================================
- Coverage   90.38%   90.35%   -0.04%     
==========================================
  Files          34       34              
  Lines        1986     1990       +4     
==========================================
+ Hits         1795     1798       +3     
- Misses        191      192       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.