Fix error on UKT emtpy user list

[sirewix]

Closes FP-243

[codecov]

Codecov Report

❌ Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 91.02%. Comparing base (13f740d) to head (01ac2ef).
⚠️ Report is 2 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/lib.rs	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #165      +/-   ##
==========================================
- Coverage   91.37%   91.02%   -0.36%     
==========================================
  Files          10       10              
  Lines        1600     1604       +4     
==========================================
- Hits         1462     1460       -2     
- Misses        138      144       +6     

Files with missing lines	Coverage Δ
src/lib.rs	79.72% <80.00%> (-0.14%)	⬇️

... and 2 files with indirect coverage changes

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