fix 400 error on /cosmos/tx/v1beta1/txs/block/ with block with no transactions

[h45hc47]

The current condition offset >= blockTxsLn incorrectly rejects valid requests when offset = 0 and blockTxsLn = 0, so on empty blocks node return error

{
    "code": 3,
    "message": "out of range: cannot paginate 0 txs with offset 0 and limit 100: invalid request: invalid request",
    "details": []
}

Changing to offset > blockTxsLn is save because:

1. Iteration bounds are protected: the actual transaction processing loops have their own bounds checking:
   • Forward pagination: i < blockTxsLn && count != limit
   • Reverse pagination: i > 0 && count != limit
2. Invalid offsets are still rejected: offsets greater than the number of transactions (like offset = 1 when blockTxsLn = 0) will still be properly rejected

Now node return valid response on empty blocks.

Issue: #3239

[cursor]

PR Summary

Low Risk
Single boundary-condition change in gRPC pagination; no auth, state, or consensus impact.

Overview
Fixes GetBlockWithTxs so /cosmos/tx/v1beta1/txs/block/ no longer returns 400 on blocks with zero transactions when offset is 0.

The out-of-range check is tightened from offset >= blockTxsLn to offset > blockTxsLn, so an empty block with default pagination is accepted and returns an empty txs list instead of "cannot paginate 0 txs with offset 0". Offsets past the tx count are still rejected; forward/reverse loops already bound iteration.

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[cursor]

Out-of-bounds panic in reverse pagination path

High Severity

Changing the guard from offset >= blockTxsLn to offset > blockTxsLn now allows offset == blockTxsLn (when non-zero) to pass through. In the reverse pagination loop, the first iteration calls decodeTxAt(offset) which accesses blockTxs[blockTxsLn] — an out-of-bounds index that causes a runtime panic. For example, a block with 5 txs and offset=5 with reverse=true would crash the node. The fix for empty blocks is correct, but needs an additional bounds check for reverse pagination when offset == blockTxsLn > 0.

Additional Locations (1)

• sei-cosmos/x/auth/tx/service.go#L219-L220

 

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