fix: remove organizer when there are no attendees

[SebastianKrupinski]

Issue

• Resolves: Error when removing invitees from event #6838

Resolution

• added logic to remove the organizer once the last attendee is removed

[SebastianKrupinski]

/backport to stable5.2

[st3iny]

Pair programming go brrrrrr

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 22.88%. Comparing base (ec93e91) to head (7d936f8).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
src/store/calendarObjectInstance.js	0.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6980      +/-   ##
============================================
- Coverage     22.89%   22.88%   -0.01%     
  Complexity      476      476              
============================================
  Files           252      252              
  Lines         12300    12303       +3     
  Branches       2372     2373       +1     
============================================
  Hits           2816     2816              
- Misses         9138     9140       +2     
- Partials        346      347       +1     

Flag	Coverage Δ
javascript	14.54% <0.00%> (-0.01%)	⬇️
php	59.33% <ø> (ø)

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

☔ 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.