Fix setting the last focus window

[hluk]

Assisted-by: Claude (Anthropic)

[codecov]

Codecov Report

❌ Patch coverage is 88.23529% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.84%. Comparing base (b234cda) to head (0d1073f).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/gui/mainwindow.cpp	85.71%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3492      +/-   ##
==========================================
- Coverage   80.85%   80.84%   -0.02%     
==========================================
  Files         245      245              
  Lines       31280    31282       +2     
==========================================
- Hits        25293    25291       -2     
- Misses       5987     5991       +4     

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

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.