fix: avoid panic when validate enum param with special matrix task

[l-qing]

fix #8464

If the matrix Task has no TaskRun to execute, the ResolvedTask will be nil, we should skip the validation.

Changes

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Release Notes

fix: avoid panic when validate enum param with special matrix task

/kind bug

[tekton-robot]

Hi @l-qing. Thanks for your PR.

I'm waiting for a tektoncd member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-pipeline-go-coverage-df to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/reconciler/pipelinerun/resources/pipelinerunresolution.go	96.2%	96.2%	0.0

[l-qing]

/retest

[tekton-robot]

@l-qing: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/retest

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[vdemeester]

/ok-to-test
cc @tektoncd/core-maintainers

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: vdemeester

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[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-pipeline-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/reconciler/pipelinerun/resources/pipelinerunresolution.go	96.2%	96.2%	0.0

[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-pipeline-go-coverage-df to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/reconciler/pipelinerun/resources/pipelinerunresolution.go	96.2%	96.2%	0.0

[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-pipeline-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/reconciler/pipelinerun/resources/pipelinerunresolution.go	96.2%	96.2%	0.0

[dibyom]

/lgtm