Avoid nil pointer deference in extractHeadlessEndpoints

[allenporter]

Description

Avoid a nil pointer deference in extractHeadlessEndpoints when TargetRef is nil. This was observed for an endpoint created by kube-prometheus-stack.

Fixes #2029

Checklist

• Unit tests updated
• End user documentation updated

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Finished.

[allenporter]

/assign @njuettner

[njuettner]

@allenporter thanks for creating a PR 👍🏻 , do you mind adding an additional test for that? I'd like to have some which covers this.

[allenporter]

@allenporter thanks for creating a PR 👍🏻 , do you mind adding an additional test for that? I'd like to have some which covers this.

Done. This is my first go change, just to set your expectations -- open to suggestions/improvements of course.

[seanmalloy]

/kind bug

[seanmalloy]

/lgtm
/assign @njuettner @Raffo

[seanmalloy]

Here is the test for the nil.

[Raffo]

/approve

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: allenporter, Raffo, seanmalloy

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