[Bug]: Build job failed to close GitHub issue because on null object.

[zelinh]

Describe the bug

The post stage of our distribution build job failed on closing GitHub issue because it pointed on null object.

opensearch-build-libraries/vars/closeBuildSuccessGithubIssue.groovy

Line 20 in ae6bcad

for (message in passMessages.unique()) {

The job ends up marking as failed even though all build and assemble are succeed and all artifacts are uploaded.
More context:

Error when executing always post condition:
Also:   org.jenkinsci.plugins.workflow.actions.ErrorAction$ErrorId: 4bfa0068-7d2e-4716-bb0f-27d9c83d6f4c
java.lang.NullPointerException: Cannot invoke method unique() on null object

https://build.ci.opensearch.org/job/distribution-build-opensearch-dashboards/7164/console

To reproduce

Run distribution build job.

Expected behavior

No response

Screenshots

If applicable, add screenshots to help explain your problem.

Host / Environment

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Additional context

No response

Relevant log output

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[rishabh6788]

Seems like the issue is fixed as we have successful OSD builds https://build.ci.opensearch.org/blue/organizations/jenkins/distribution-build-opensearch-dashboards/detail/distribution-build-opensearch-dashboards/7295/pipeline

See https://github.com/opensearch-project/opensearch-build-libraries/blob/main/vars/UpdateBuildFailureIssues.groovy#L31-L35