KObjSlice: nil entry printed as ""

[pohly]

/kind bug

What steps did you take and what happened:

I added a test in https://github.com/kubernetes/kubernetes/pull/125699/files

logger.Info("Some NodeInfo slice", "nodes", klog.KObjSlice([]*NodeInfo{nil, {}, {node: &v1.Node{}}, {node: &v1.Node{ObjectMeta: metav1.ObjectMeta{Name: "worker"}}}}))

*NodeInfo implements klog.KMetadata. The first slice entry is passed to klog.KObj which detects the nil value and turns it into an empty ObjectRef{}. That then gets printed as "" in the array.

What did you expect to happen:

Some kind of indicator that the first entry is nil.

[dgrisonnet]

/triage accepted
/help

I am leaving it help wanted for now

[k8s-ci-robot]

@dgrisonnet:
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In response to this:

/triage accepted
/help

I am leaving it help wanted for now

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