fix: possible overflow in BuildUnsignedTx (backport #1303)

[mergify[bot]]

Description

• (audit issue) fix possible overflow in BuildUnsignedTx
  • referenced implementation(https://github.com/cosmos/cosmos-sdk/pull/18622)

Motivation and context

How has this been tested?

Screenshots (if appropriate):

Checklist:

• [x] I followed the contributing guidelines and code of conduct.
• [x] I have added a relevant changelog to CHANGELOG.md
• [ ] I have added tests to cover my changes.
• [ ] I have updated the documentation accordingly.
• [ ] I have updated API documentation client/docs/swagger-ui/swagger.yaml

  ---

  This is an automatic backport of pull request #1303 done by Mergify.

[mergify[bot]]

Cherry-pick of b1c09cf6c82b9db4600176512ecf5e1b14679385 has failed:

On branch mergify/bp/release/v0.48.x/pr-1303
Your branch is up to date with 'origin/release/v0.48.x'.

You are currently cherry-picking commit b1c09cf6c.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
    modified:   client/tx/factory.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
    both modified:   CHANGELOG.md

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 69.78%. Comparing base (8e8a284) to head (8cd3f6b).

Additional details and impacted files

[](https://app.codecov.io/gh/Finschia/finschia-sdk/pull/1307?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Finschia) ```diff @@ Coverage Diff @@ ## release/v0.48.x #1307 +/- ## ================================================ Coverage 69.78% 69.78% ================================================ Files 646 646 Lines 67526 67526 ================================================ Hits 47126 47126 Misses 18214 18214 Partials 2186 2186 ``` | [Files](https://app.codecov.io/gh/Finschia/finschia-sdk/pull/1307?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Finschia) | Coverage Δ | | |---|---|---| | [client/tx/factory.go](https://app.codecov.io/gh/Finschia/finschia-sdk/pull/1307?src=pr&el=tree&filepath=client%2Ftx%2Ffactory.go&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Finschia#diff-Y2xpZW50L3R4L2ZhY3RvcnkuZ28=) | `60.50% <100.00%> (ø)` | |