fix(x/ecocredit): replace blank event values with actual values

[technicallyty]

Description

replaces values in events that were previously empty strings "", to the dec zero value "0".

Closes: #1333

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Author Checklist

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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

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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

❗ No coverage uploaded for pull request base (main@cf16e04). Click here to learn what that means.
The diff coverage is 85.71%.

❗ Current head 681c82a differs from pull request most recent head bcbe387. Consider uploading reports for the commit bcbe387 to get more accurate results

@@           Coverage Diff           @@
##             main    #1411   +/-   ##
=======================================
  Coverage        ?   75.32%           
=======================================
  Files           ?      223           
  Lines           ?    20830           
  Branches        ?        0           
=======================================
  Hits            ?    15690           
  Misses          ?     4185           
  Partials        ?      955           

Impacted Files	Coverage Δ
x/ecocredit/server/core/msg_send.go	69.17% <76.92%> (ø)
x/ecocredit/server/core/msg_create_batch.go	66.32% <100.00%> (ø)
x/ecocredit/server/core/msg_mint_batch_credits.go	56.00% <100.00%> (ø)

[ryanchristo]

small fix but changelog entry would be nice 🙏

[ryanchristo]

LGTM