Fix index out of bounds error when building status (#3513)

[sjberman]

Cherrypick of #3513

Problem: There's a specific scenario where we can hit an out of bounds index while building route statuses. I don't know the exact scenario, but it involves a parentRef without a sectionName, on a Gateway with a single listener. Could possibly involve having multiple implementations being deployed as well.

Solution: Adjust the logic to ensure we don't access indices that are out of bounds.

Testing: Verified that this error does not occur in the previous scenario.

Checklist

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• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

Release notes

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please add a brief note that summarizes the change.

Fix index out of bounds error when building status

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.19%. Comparing base (fdb1b60) to head (7eb6518).
Report is 1 commits behind head on release-2.0.

Additional details and impacted files

@@               Coverage Diff               @@
##           release-2.0    #3576      +/-   ##
===============================================
+ Coverage        86.81%   95.19%   +8.38%     
===============================================
  Files              127        1     -126     
  Lines            15079      229   -14850     
  Branches            62       62              
===============================================
- Hits             13091      218   -12873     
+ Misses            1837       11    -1826     
+ Partials           151        0     -151     

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