client/http: fix the scan region parameter

[Smityz]

What problem does this PR solve?

Issue Number: Close #7869

What is changed and how does it work?

add null pointer check and fix http request format

Check List

Tests

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

Code changes

• Has the configuration change
• Has HTTP API interfaces changed (Don't forget to add the declarative for the new API)
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• PR to update pingcap/tiup:
• Need to cherry-pick to the release branch

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• JmPotato
• rleungx

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

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

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[ti-chi-bot]

Hi @Smityz. Thanks for your PR.

I'm waiting for a tikv member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[codecov]

Codecov Report

Merging #7870 (cf23605) into master (2851db2) will increase coverage by 0.03%.
The diff coverage is 33.33%.

❗ Current head cf23605 differs from pull request most recent head f0a23c3. Consider uploading reports for the commit f0a23c3 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7870      +/-   ##
==========================================
+ Coverage   73.44%   73.48%   +0.03%     
==========================================
  Files         433      432       -1     
  Lines       47972    47968       -4     
==========================================
+ Hits        35235    35248      +13     
+ Misses       9691     9670      -21     
- Partials     3046     3050       +4     

Flag	Coverage Δ
unittests	73.48% <33.33%> (+0.03%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

[JmPotato]

The rest LGTM.

[JmPotato]

/merge

[ti-chi-bot]

@JmPotato: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

You only need to trigger /merge once, and if the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

If you have any questions about the PR merge process, please refer to pr process.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: f0a23c3

[JmPotato]

/check-issue-triage-complete