[stable5.3] fix(free-busy): close modal when all attendees removed

[backportbot]

Backport of PR #7025

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 22.86%. Comparing base (c038286) to head (159ddfd).
Report is 4 commits behind head on stable5.3.

Files with missing lines	Patch %	Lines
src/components/Editor/Invitees/InviteesList.vue	0.00%	1 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##             stable5.3    #7027      +/-   ##
===============================================
- Coverage        22.87%   22.86%   -0.02%     
  Complexity         476      476              
===============================================
  Files              252      252              
  Lines            12311    12318       +7     
  Branches          2380     2382       +2     
===============================================
  Hits              2816     2816              
- Misses            9147     9154       +7     
  Partials           348      348              

Flag	Coverage Δ
javascript	14.52% <0.00%> (-0.02%)	⬇️
php	59.33% <ø> (ø)

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