Failed to update status for ... Sequence is invalid: ... status.subscriptionStatuses.ready.lastTransitionTime in body must be of type string: "null"

[maschmid]

Describe the bug

When creating a Sequence, it sometimes creates an UpdateFailed event saying

Failed to update status for "sequence": Sequence.flows.knative.dev "sequence" is invalid: [status.channelStatuses.ready.lastTransitionTime: Invalid value: "null": status.channelStatuses.ready.lastTransitionTime in body must be of type string: "null", status.subscriptionStatuses.ready.lastTransitionTime: Invalid value: "null": status.subscriptionStatuses.ready.lastTransitionTime in body must be of type string: "null"]

Expected behavior Controller should not fail to update status, even if the Channel Ready status doesn't have a transition time yet (or whatever the problem actually is)

To Reproduce Deploy a Sequence example. It feels more reproducible with a channel implementation that is slower to become Ready (e.g. a KafkaChannel), but I have seen this with IMC as well: e.g. a variant with InMemoryChannel, https://gist.github.com/maschmid/6a8debcc73d8dbdabe4c9c38d7a57517

Knative release version 1.1.0

Additional context knative installed via OpenShift Serverless Operator 1.22.0