[cherry-pick] panic due to mark retention task error

[stonezdj]

fixes #20129

Thank you for contributing to Harbor!

Comprehensive Summary of your change

Issue being fixed

Fixes #(issue)

Please indicate you've done the following:

• Well Written Title and Summary of the PR
• Label the PR as needed. "release-note/ignore-for-release, release-note/new-feature, release-note/update, release-note/enhancement, release-note/community, release-note/breaking-change, release-note/docs, release-note/infra, release-note/deprecation"
• Accepted the DCO. Commits without the DCO will delay acceptance.
• Made sure tests are passing and test coverage is added if needed.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed in website repository.

[codecov]

Codecov Report

Attention: Patch coverage is 42.85714% with 16 lines in your changes are missing coverage. Please review.

Project coverage is 67.38%. Comparing base (fcc7ae4) to head (11f5120).

Additional details and impacted files

@@                Coverage Diff                @@
##           release-2.8.0   #20168      +/-   ##
=================================================
+ Coverage          67.35%   67.38%   +0.02%     
=================================================
  Files                984      984              
  Lines             107094   107102       +8     
  Branches            2671     2671              
=================================================
+ Hits               72134    72169      +35     
+ Misses             31078    31055      -23     
+ Partials            3882     3878       -4     

Flag	Coverage Δ
unittests	67.38% <42.85%> (+0.02%)	⬆️

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

Files	Coverage Δ
src/controller/retention/controller.go	48.26% <0.00%> (+0.62%)	⬆️
src/controller/replication/execution.go	70.65% <0.00%> (+1.24%)	⬆️
src/controller/systemartifact/execution.go	75.28% <0.00%> (+2.45%)	⬆️
src/pkg/task/dao/task.go	64.31% <80.00%> (+0.10%)	⬆️
src/pkg/task/execution.go	65.04% <0.00%> (-2.39%)	⬇️

... and 7 files with indirect coverage changes

[wy65701436]

lgtm