fix: Fixed NPE while getting the ReplicaSet labels

[agrawroh]

Description

This PR fixes a NPE which gets thrown while getting the ReplicaSet labels if the RS itself is null. See #1630 for more details.

Checklist

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this is a chore.
• The title of the PR is (a) conventional, (b) states what changed, and (c) suffixes the related issues number. E.g. "fix(controller): Updates such and such. Fixes #1234".
• I've signed my commits with DCO
• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• My builds are green. Try syncing with master if they are not.
• My organization is added to USERS.md.

---

Signed-off-by: Rohit Agrawal rohit.agrawal@databricks.com

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
7.1% Duplication

[codecov]

Codecov Report

Merging #1664 (2572a7a) into master (6edc9c8) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1664      +/-   ##
==========================================
- Coverage   81.99%   81.97%   -0.02%     
==========================================
  Files         115      115              
  Lines       15913    15913              
==========================================
- Hits        13048    13045       -3     
- Misses       2196     2198       +2     
- Partials      669      670       +1     

Impacted Files	Coverage Δ
utils/replicaset/replicaset.go	90.04% <100.00%> (ø)
rollout/trafficrouting/istio/controller.go	50.81% <0.00%> (-1.63%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6edc9c8...2572a7a. Read the comment docs.

[alexmt]

LGTM