cdc: fixes minor bugs #10168 and #10169 (#10170)

[hicqu]

What problem does this PR solve?

Issue Number: close #xxx

What is changed and how it works?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Questions

Will it cause performance regression or break compatibility?

Do you need to update user documentation, design documentation or monitoring documentation?

Release note

Please refer to [Release Notes Language Style Guide](https://pingcap.github.io/tidb-dev-guide/contribute-to-tidb/release-notes-style-guide.html) to write a quality release note.

If you don't think this PR needs a release note then fill it with `None`.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: asddongmen, nongfushanquan

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [asddongmen]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-12-04 03:00:19.194593539 +0000 UTC m=+1410047.859819734: ☑️ agreed by nongfushanquan.
• 2023-12-07 04:59:49.527090884 +0000 UTC m=+1676418.192317073: ☑️ agreed by asddongmen.