fix: update param validation to fail on nil dec

[jaeseung-bae]

Description

• fix: update param validation to fail on nil dec
  • refer: https://github.com/cosmos/cosmos-sdk/pull/13553

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

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 14 lines in your changes are missing coverage. Please review.

Project coverage is 70.38%. Comparing base (c051dcc) to head (1dba6ec).

Additional details and impacted files

[](https://app.codecov.io/gh/Finschia/finschia-sdk/pull/1323?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Finschia) ```diff @@ Coverage Diff @@ ## main #1323 +/- ## ========================================== - Coverage 70.39% 70.38% -0.02% ========================================== Files 643 643 Lines 54779 54793 +14 ========================================== + Hits 38563 38564 +1 - Misses 14041 14054 +13 Partials 2175 2175 ``` | [Files](https://app.codecov.io/gh/Finschia/finschia-sdk/pull/1323?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Finschia) | Coverage Δ | | |---|---|---| | [x/slashing/types/params.go](https://app.codecov.io/gh/Finschia/finschia-sdk/pull/1323?src=pr&el=tree&filepath=x%2Fslashing%2Ftypes%2Fparams.go&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Finschia#diff-eC9zbGFzaGluZy90eXBlcy9wYXJhbXMuZ28=) | `0.00% <0.00%> (ø)` | | | [x/mint/types/params.go](https://app.codecov.io/gh/Finschia/finschia-sdk/pull/1323?src=pr&el=tree&filepath=x%2Fmint%2Ftypes%2Fparams.go&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Finschia#diff-eC9taW50L3R5cGVzL3BhcmFtcy5nbw==) | `7.40% <0.00%> (-0.60%)` | :arrow_down: | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/Finschia/finschia-sdk/pull/1323/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Finschia)

[170210]

~Is it necessary to add the same contents under x/distribution? There are three similar bugs under x/distribution.~

[jaeseung-bae]

Is it necessary to add the same contents under x/distribution? There are three similar bugs under x/distribution.

I can't find any in x/distribution, could you share the points?

[170210]

I can't find any in x/distribution, could you share the points?

Sorry, I made a mistake. There's no problem under x/distribution...