fix: validate decimals before conversion to prevent panic in GetBaseFee

[mmsqe]

Description

Closes: #XXXX

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Author Checklist

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please add links to any relevant follow up issues.

I have...

• tackled an existing issue or discussed with a team member
• left instructions on how to review the changes
• targeted the main branch

[codecov]

Codecov Report

❌ Patch coverage is 63.63636% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 65.22%. Comparing base (cd4f406) to head (28b31f8).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
x/vm/wrappers/feemarket.go	63.63%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #828      +/-   ##
==========================================
+ Coverage   64.97%   65.22%   +0.25%     
==========================================
  Files         317      317              
  Lines       21607    21612       +5     
==========================================
+ Hits        14039    14097      +58     
- Misses       6348     6352       +4     
+ Partials     1220     1163      -57     

Files with missing lines	Coverage Δ
x/vm/wrappers/feemarket.go	85.18% <63.63%> (-14.82%)	⬇️

... and 6 files with indirect coverage changes

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