fix: avoid nil pointer dereference and remove redundant code

[okaybase]

Please answer these questions before submitting a pull request, or your PR will get closed.

Why submit this pull request?

• Bugfix
• New feature provided
• Improve performance
• Backport patches

What changes will this PR take into?

Please update this section with detailed description.

Related issues

fix/resolve:

1. avoid nil pointer dereference
2. remove redundant code

Checklist:

• Did you explain what problem does this PR solve? Or what new features have been added?
• Have you added corresponding test cases?
• Have you modified the corresponding document?
• Is this PR backward compatible? If it is not backward compatible, please discuss on the mailing list first

[netlify]

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[codecov-commenter]

Codecov Report

Merging #2031 (2291022) into master (fe6e155) will increase coverage by 3.94%.
The diff coverage is 66.66%.

❗ Current head 2291022 differs from pull request most recent head b48c84f. Consider uploading reports for the commit b48c84f to get more accurate results

@@            Coverage Diff             @@
##           master    #2031      +/-   ##
==========================================
+ Coverage   64.03%   67.98%   +3.94%     
==========================================
  Files         121      181      +60     
  Lines        3156     6971    +3815     
  Branches      753      753              
==========================================
+ Hits         2021     4739    +2718     
- Misses       1135     1946     +811     
- Partials        0      286     +286     

Flag	Coverage Δ
backend-e2e-test	46.97% <66.66%> (?)
backend-e2e-test-ginkgo	49.33% <0.00%> (?)
backend-unit-test	53.24% <66.66%> (?)
frontend-e2e-test	64.03% <ø> (ø)

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

Impacted Files	Coverage Δ
api/internal/handler/data_loader/route_export.go	75.00% <66.66%> (ø)
api/internal/core/store/store.go	89.47% <0.00%> (ø)
api/internal/core/store/store_mock.go	0.00% <0.00%> (ø)
api/internal/handler/consumer/consumer.go	92.06% <0.00%> (ø)
api/internal/filter/schema.go	56.00% <0.00%> (ø)
api/internal/handler/label/label.go	86.20% <0.00%> (ø)
api/internal/utils/runtime/runtime.go	66.66% <0.00%> (ø)
api/internal/core/storage/etcd.go	51.18% <0.00%> (ø)
api/internal/filter/recover.go	7.69% <0.00%> (ø)
api/internal/utils/pid.go	42.85% <0.00%> (ø)
... and 51 more

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