KubeFed controller stop working when there are KubeFedClusters with malformed configs whose previous status is ready

[zqzten]

What happened:
We accidentally deleted a Secret of one KubeFedCluster which is ready previously. After that, we found that KubeFed controller stop working due to an informer sync check error The number of target informers mismatch with given clusters. This is because the KubeFedCluster with malformed config is still in Ready state but the controller cannot create a REST client for it.

What you expected to happen:
KubeFedClusters with malformed config should turn into a non-ready condition in order not to block the whole controller.

How to reproduce it (as minimally and precisely as possible):
Delete any ready KubeFedCluster's Secret then restart KubeFed controller.

/kind bug

[zqzten]

/assign

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/lifecycle stale

[zqzten]

/remove-lifecycle stale