[FLINK-34954][core] Kryo Input bug fix

[qinghui-xu]

Handle edge case of zero length serialized bytes correctly.

What is the purpose of the change

Bug fix in kryo (NoFetching)Input implementation to handle properly zero length serialized bytes, eg the serialization of a protobuf message with default values.

Brief change log

• Fix while loop for NoFetchingInput#read(byte[], int, int) and NoFetchingInput#require(int)

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: yes
• The runtime per-record code paths (performance sensitive): yes
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no

[flinkbot]

CI report:

• a37e562 Azure: SUCCESS

Bot commands

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[qinghui-xu]

Hello team,
Could I get a review for this, please?

[dannycranmer]

LGTM, thanks @qinghui-xu

[davidradl]

@dannycranmer I saw this linked to in slack - I wondered whether we could have junits for the required case and higher than required? Maybe as a follow on issue / pr ? I could code if you were willing to merge for me?

[dmvk]

Why is this not covered with a regression test? That feels rather scary in such a critical part of the stack.