fix eth_estimateGas panic

[owahlgren]

Description

eth_estimateGas panics with nil reference if arg param is nil ie
{ "jsonrpc":"2.0", "method":"eth_estimateGas", "params":[], "id":1 }
this change catches nil arg and throws appropriate error

Changes include

• Bugfix (non-breaking change that solves an issue)
• Hotfix (change that solves an urgent issue, and requires immediate attention)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)

Checklist

• I have assigned this PR to myself
• I have added at least 1 reviewer
• I have added the relevant labels
• I have updated the official documentation
• I have added sufficient documentation in code

Testing

• [ x] I have tested this code with the official test suite
• [ x] I have tested this code manually

Manual tests

curl -X POST --data '{"jsonrpc":"2.0","method":"eth_estimateGas","params":[],"id":1}' http://localhost:10002
now returns
"message": "missing value for required argument 0"

[github-actions]

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

[owahlgren]

I have read the CLA Document and I hereby sign the CLA

[vcastellm]

Due to Goran's comment