fix yurtappoverrider panic for handling normal deployments that has no ownerreferences

[rambohe-ch]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:
/kind bug
/kind documentation
/kind enhancement
/kind good-first-issue
/kind feature
/kind question
/kind design
/sig ai
/sig iot
/sig network
/sig storage

/kind bug

What this PR does / why we need it:

panic will happen in yurtappoverrider when ordinary deployments without ownerreferences are handled.
so ownerreferences should be checked before yurtapporverrider deals with it.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

other Note

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In response to this:

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:
/kind bug
/kind documentation
/kind enhancement
/kind good-first-issue
/kind feature
/kind question
/kind design
/sig ai
/sig iot
/sig network
/sig storage

/kind bug

What this PR does / why we need it:

panic will happen in yurtappoverrider when ordinary deployments without ownerreferences are handled.
so ownerreferences should be checked before yurtapporverrider deals with it.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

other Note

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[rambohe-ch]

@vie-serendipity @YTGhost PTAL

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
1.1% Duplication

[codecov]

Codecov Report

Merging #1730 (3b71d0c) into master (c4aac68) will decrease coverage by 0.06%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master    #1730      +/-   ##
==========================================
- Coverage   50.79%   50.73%   -0.06%     
==========================================
  Files         165      165              
  Lines       19248    19249       +1     
==========================================
- Hits         9777     9766      -11     
- Misses       8554     8565      +11     
- Partials      917      918       +1     

Flag	Coverage Δ
unittests	50.73% <66.66%> (-0.06%)	⬇️

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

Files	Coverage Δ
...er/yurtappoverrider/yurtappoverrider_controller.go	32.60% <66.66%> (+0.74%)	⬆️

... and 1 file with indirect coverage changes

[YTGhost]

/lgtm

[openyurt-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: rambohe-ch, YTGhost

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