[ilcm96]

What type of PR is this?

/kind bug

What this PR does / why we need it:

In the watch path of Watch.stream(), unmarshal_event() returns None for a blank or undecodable line, and stream() treats it as an event:

• It yields None, so SharedInformer fails on event.get("type") and DynamicClient.watch() fails on event['object'].
• It resets the one-time 410 retry. If every response has a blank line before a 410 Gone ERROR, a watch without timeout_seconds reconnects forever with the expired resourceVersion.

E.g. a response of "\n" followed by an ADDED event yields [None, {...}].

This PR skips None instead of yielding it or resetting the retry, and still checks stop() after a skipped line. The log/follow path still yields empty lines (#2372).

Which issue(s) this PR fixes:

None.

Special notes for your reviewer:

• kubernetes.aio Watch has its own line handling and is not changed here.
• Tested with new unit tests in kubernetes/watch/watch_test.py; the watch-path tests fail on master. A real API server does not send blank lines, so on a kind cluster I only ran the existing watch/informer e2e tests as a regression check.

Does this PR introduce a user-facing change?

`Watch.stream()` no longer yields `None` for blank or undecodable watch lines, and such lines no longer reset the one-time retry after a 410 Gone error.

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[kubernetes-prow]

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This pull-request has been approved by: ilcm96
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