Optimizing the use of orLabelSelectors to get resources

[learner0810]

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Please add a summary of your change

If an error occurs when using orLabelSelectors to fetch resources, unstructuredItems will not be added to the items, so the loop will simply jump out of the loop when an error occurs.

Does your change fix a particular issue?

Fixes #(issue)

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• Accepted the DCO. Commits without the DCO will delay acceptance.
• Created a changelog file or added /kind changelog-not-required as a comment on this pull request.
• Updated the corresponding documentation in site/content/docs/main.

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (f109f38) 61.73% compared to head (a9c3b72) 61.71%.
Report is 6 commits behind head on main.

Files	Patch %	Lines
pkg/backup/item_collector.go	66.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7256      +/-   ##
==========================================
- Coverage   61.73%   61.71%   -0.03%     
==========================================
  Files         262      262              
  Lines       28428    28421       -7     
==========================================
- Hits        17551    17539      -12     
- Misses       9645     9650       +5     
  Partials     1232     1232              

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[blackpiglet]

The Velero v1.13 is on the way. We'd better wait for the release-1.13 branch cut to merge this PR.

[blackpiglet]

Although, after modification, there should be no unstructed object found when listing with or label selector, it's better to have an early return.