fix: GetBlockWithTxs error when querying block with 0 tx (#12108)

## Description

Closes: https://github.com/cosmos/cosmos-sdk/issues/12040



---

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- [ ] added a changelog entry to `CHANGELOG.md`
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- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
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CHANGELOG.md

@@ -50,6 +50,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (migrations) [#12028](https://github.com/cosmos/cosmos-sdk/pull/12028) Fix v0.45->v0.46 in-place store migrations.
 * (baseapp) [#12089](https://github.com/cosmos/cosmos-sdk/pull/12089) Include antehandler and runMsgs events in SimulateTx.
 * (cli) [#12095](https://github.com/cosmos/cosmos-sdk/pull/12095) Fix running a tx with --dry-run returns an error
+* (x/auth) [#12108](https://github.com/cosmos/cosmos-sdk/pull/12108) Fix GetBlockWithTxs error when querying block with 0 tx
 
 ## [v0.46.0-rc1](https://github.com/cosmos/cosmos-sdk/releases/tag/v0.46.0-rc1) - 2022-05-23
 

x/auth/tx/service.go

@@ -198,7 +198,7 @@ func (s txServer) GetBlockWithTxs(ctx context.Context, req *txtypes.GetBlockWith
 	blockTxs := block.Data.Txs
 	blockTxsLn := uint64(len(blockTxs))
 	txs := make([]*txtypes.Tx, 0, limit)
-	if offset >= blockTxsLn {
+	if offset >= blockTxsLn && blockTxsLn != 0 {
 		return nil, sdkerrors.ErrInvalidRequest.Wrapf("out of range: cannot paginate %d txs with offset %d and limit %d", blockTxsLn, offset, limit)
 	}
 	decodeTxAt := func(i uint64) error {

x/auth/tx/service_test.go

@@ -615,14 +615,16 @@ func (s IntegrationTestSuite) TestGetBlockWithTxs_GRPC() {
 		req       *tx.GetBlockWithTxsRequest
 		expErr    bool
 		expErrMsg string
+		expTxsLen int
 	}{
-		{"nil request", nil, true, "request cannot be nil"},
-		{"empty request", &tx.GetBlockWithTxsRequest{}, true, "height must not be less than 1 or greater than the current height"},
-		{"bad height", &tx.GetBlockWithTxsRequest{Height: 99999999}, true, "height must not be less than 1 or greater than the current height"},
-		{"bad pagination", &tx.GetBlockWithTxsRequest{Height: s.txHeight, Pagination: &query.PageRequest{Offset: 1000, Limit: 100}}, true, "out of range"},
-		{"good request", &tx.GetBlockWithTxsRequest{Height: s.txHeight}, false, ""},
-		{"with pagination request", &tx.GetBlockWithTxsRequest{Height: s.txHeight, Pagination: &query.PageRequest{Offset: 0, Limit: 1}}, false, ""},
-		{"page all request", &tx.GetBlockWithTxsRequest{Height: s.txHeight, Pagination: &query.PageRequest{Offset: 0, Limit: 100}}, false, ""},
+		{"nil request", nil, true, "request cannot be nil", 0},
+		{"empty request", &tx.GetBlockWithTxsRequest{}, true, "height must not be less than 1 or greater than the current height", 0},
+		{"bad height", &tx.GetBlockWithTxsRequest{Height: 99999999}, true, "height must not be less than 1 or greater than the current height", 0},
+		{"bad pagination", &tx.GetBlockWithTxsRequest{Height: s.txHeight, Pagination: &query.PageRequest{Offset: 1000, Limit: 100}}, true, "out of range", 0},
+		{"good request", &tx.GetBlockWithTxsRequest{Height: s.txHeight}, false, "", 1},
+		{"with pagination request", &tx.GetBlockWithTxsRequest{Height: s.txHeight, Pagination: &query.PageRequest{Offset: 0, Limit: 1}}, false, "", 1},
+		{"page all request", &tx.GetBlockWithTxsRequest{Height: s.txHeight, Pagination: &query.PageRequest{Offset: 0, Limit: 100}}, false, "", 1},
+		{"block with 0 tx", &tx.GetBlockWithTxsRequest{Height: s.txHeight - 1, Pagination: &query.PageRequest{Offset: 0, Limit: 100}}, false, "", 0},
 	}
 	for _, tc := range testCases {
 		s.Run(tc.name, func() {
@@ -633,7 +635,9 @@ func (s IntegrationTestSuite) TestGetBlockWithTxs_GRPC() {
 				s.Require().Contains(err.Error(), tc.expErrMsg)
 			} else {
 				s.Require().NoError(err)
-				s.Require().Equal("foobar", grpcRes.Txs[0].Body.Memo)
+				if tc.expTxsLen > 0 {
+					s.Require().Equal("foobar", grpcRes.Txs[0].Body.Memo)
+				}
 				s.Require().Equal(grpcRes.Block.Header.Height, tc.req.Height)
 				if tc.req.Pagination != nil {
 					s.Require().LessOrEqual(len(grpcRes.Txs), int(tc.req.Pagination.Limit))