Fix Panic in the API server

[khrm]

API server gets panic under certain negative scenarios. We fixed that by creating a new variable for error.

Changes

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Release Notes

[khrm]

/assign @enarha @vdemeester

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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[enarha]

/lgtm

[khrm]

/chery-pick @release-v0.12.x

[khrm]

/chery-pick release-v0.12.x

[khrm]

/cherry-pick release-v0.12.x

[tekton-robot]

@khrm: new pull request created: #872

In response to [this](https://github.com/tektoncd/results/pull/870#issuecomment-2455242988): >/cherry-pick release-v0.12.x > > Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.

[khrm]

/cherry-pick release-v0.12.x

[tekton-robot]

@khrm: new pull request could not be created: failed to create pull request against tektoncd/results#release-v0.12.x from head tekton-robot:cherry-pick-870-to-release-v0.12.x: status code 422 not one of [201], body: {"message":"Validation Failed","errors":[{"resource":"PullRequest","code":"custom","message":"A pull request already exists for tekton-robot:cherry-pick-870-to-release-v0.12.x."}],"documentation_url":"https://docs.github.com/rest/pulls/pulls#create-a-pull-request","status":"422"}

In response to [this](https://github.com/tektoncd/results/pull/870#issuecomment-2455245173): > >/cherry-pick release-v0.12.x > > Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.