fix(x/ecocredit): remove fee param when amount is zero

[aleem1314]

Description

Closes: #1597

---

Author Checklist

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.

I have...

• included the correct type prefix in the PR title
• added ! to the type prefix if API or client breaking change
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• followed the guidelines for building modules
• included the necessary unit and integration tests
• added a changelog entry to CHANGELOG.md
• included comments for documenting Go code
• updated the relevant documentation or specification
• reviewed "Files changed" and left comments if necessary
• confirmed all CI checks have passed

Reviewers Checklist

All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.

I have...

• confirmed the correct type prefix in the PR title
• confirmed ! in the type prefix if API or client breaking change
• confirmed all author checklist items have been addressed
• reviewed state machine logic
• reviewed API design and naming
• reviewed documentation is accurate
• reviewed tests and test coverage
• manually tested (if applicable)

[codecov]

Codecov Report

Merging #1604 (8e049a4) into main (1b52730) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 8e049a4 differs from pull request most recent head 6ebf6ca. Consider uploading reports for the commit 6ebf6ca to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1604   +/-   ##
=======================================
  Coverage   77.53%   77.53%           
=======================================
  Files         264      264           
  Lines       19288    19288           
=======================================
  Hits        14954    14954           
  Misses       3469     3469           
  Partials      865      865           

Impacted Files	Coverage Δ
x/ecocredit/base/keeper/msg_update_class_fee.go	78.57% <100.00%> (ø)
x/ecocredit/basket/keeper/msg_update_basket_fee.go	80.00% <100.00%> (ø)

[technicallyty]

ACK

[ryanchristo]

LGTM