fix(evmrpc): return null for out-of-range index in eth_getTransactionByBlock*AndIndex

[amir-deris]

Summary

• eth_getTransactionByBlockNumberAndIndex and eth_getTransactionByBlockHashAndIndex were returning a JSON-RPC error when the requested transaction index exceeded the number of transactions in the block.
• Per the Ethereum JSON-RPC spec, these methods must return null (not an error) when no transaction exists at the given index.
• Changed getTransactionWithBlock to return (nil, nil) instead of (nil, error) on out-of-range index, and updated the corresponding test.

[github-actions]

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Apr 30, 2026, 4:10 PM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.17%. Comparing base (10c2d92) to head (b08463b).
⚠️ Report is 19 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3320   +/-   ##
=======================================
  Coverage   59.16%   59.17%           
=======================================
  Files        2093     2093           
  Lines      171972   171990   +18     
=======================================
+ Hits       101755   101773   +18     
  Misses      61401    61401           
  Partials     8816     8816           

Flag	Coverage Δ
sei-chain-pr	64.52% <100.00%> (?)
sei-db	70.41% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
evmrpc/tx.go	85.01% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[masih]

/backport

[seidroid]

Successfully created backport PR for release/v6.5:

• Backport release/v6.5: fix(evmrpc): return null for out-of-range index in eth_getTransactionByBlock*AndIndex #3367