[release-1.16] make array when filters is nil

[knative-prow-robot]

This is an automated cherry-pick of #2569

[codecov]

Codecov Report

Attention: Patch coverage is 25.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 65.39%. Comparing base (462cdc2) to head (e9b577d).
Report is 1 commits behind head on release-1.16.

Files with missing lines	Patch %	Lines
cmd/subscribe.go	25.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.16    #2571      +/-   ##
================================================
+ Coverage         64.14%   65.39%   +1.25%     
================================================
  Files               130      130              
  Lines             15479    15482       +3     
================================================
+ Hits               9929    10125     +196     
+ Misses             4614     4382     -232     
- Partials            936      975      +39     

Flag	Coverage Δ
e2e-test	35.90% <0.00%> (+0.01%)	⬆️
e2e-test-oncluster	32.88% <0.00%> (+0.02%)	⬆️
e2e-test-oncluster-runtime	28.64% <0.00%> (?)
e2e-test-runtime-go	26.45% <0.00%> (?)
e2e-test-runtime-node	25.85% <0.00%> (?)
e2e-test-runtime-python	25.85% <0.00%> (?)
e2e-test-runtime-quarkus	26.00% <0.00%> (?)
e2e-test-runtime-rust	25.01% <0.00%> (?)
e2e-test-runtime-springboot	25.05% <0.00%> (?)
e2e-test-runtime-typescript	25.96% <0.00%> (?)
integration-tests	51.92% <25.00%> (+2.30%)	⬆️
unit-tests	50.87% <25.00%> (?)
unit-tests-macos-latest	?
unit-tests-ubuntu-latest	?
unit-tests-windows-latest	?

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[matejvasek]

/approve
/lgtm

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

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