[FLINK-27741][table-planner] Fix NPE when use dense_rank() and rank()…

[chenzihao5]

Fix NPE when use dense_rank() and rank() in over aggregation.

What is the purpose of the change

This pull request fixes NullPointException when use DENSE_RANK() and RANK() for an append stream.

Brief change log

• Judge the null value
• Add ITCase for DENSE_RANK and RANK

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: no
• The runtime per-record code paths (performance sensitive): no
• 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
• If yes, how is the feature documented? not applicable

[flinkbot]

CI report:

• 88731c59969636f24743c9f596633fdd5ad7cbd8 Azure: SUCCESS

Bot commands

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• @flinkbot run azure re-run the last Azure build

[snuyanzin]

@chenzihao5 thanks for your contribution and sorry for the late reply

May i ask you to rebase and then we can make another review iteration?

[snuyanzin]

There is no response from the author, so I addressed feedback (the initial author is still in git history)

@xuyangzhong could you please have a look once again?

[snuyanzin]

Thanks for the review @xuyangzhong