[release-v0.22.x] fix nil pointer

[tekton-robot]

This is an automated cherry-pick of #1248

/assign jkhelil

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In response to this:

This is an automated cherry-pick of #1248

/assign jkhelil

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[tekton-robot]

@tekton-robot: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-tekton-chains-integration-tests	2604533	link	true	/test pull-tekton-chains-integration-tests

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[jkhelil]

@afrittoli @vdemeester e2e tests are failing and seems related to the latest work on ci/plumbing
Can you have a look please

[jkhelil]

@tektoncd/chains-maintainers this should be closed, please