fix: filtered pagination NextKey off-by-one when Offset != 0 and CountTotal == true (#11408)

## Description

Closes: [#11407](https://github.com/cosmos/cosmos-sdk/issues/11407)



In the original code, when CountTotal == true, the iteration goes even after the `end+1`-th hit.

The `end+1`-th hit is expected to be `NextKey`. However, if there is a no-hit after after that, `numHits == end+1` is still true, and `NextKey` will be set to key beyond the `end+1`-th hit, resulting in consecutive queries missing the `end+1`-th hit.

---

### Author Checklist

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- [ ] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
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- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
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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
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
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- [ ] manually tested (if applicable)

types/query/filtered_pagination.go

@@ -98,7 +98,9 @@ func FilteredPaginate(
 		}
 
 		if numHits == end+1 {
-			nextKey = iterator.Key()
+			if nextKey == nil {
+				nextKey = iterator.Key()
+			}
 
 			if !countTotal {
 				break

types/query/filtered_pagination_test.go

@@ -253,3 +253,66 @@ func execFilterPaginate(store sdk.KVStore, pageReq *query.PageRequest, appCodec
 
 	return balResult, res, err
 }
+
+func (s *paginationTestSuite) TestFilteredPaginationsNextKey() {
+	app, ctx, appCodec := setupTest(s.T())
+
+	var balances sdk.Coins
+
+	for i := 1; i <= 10; i++ {
+		denom := fmt.Sprintf("test%ddenom", i)
+		balances = append(balances, sdk.NewInt64Coin(denom, int64(i)))
+	}
+
+	balances = balances.Sort()
+	addr1 := sdk.AccAddress([]byte("addr1"))
+	acc1 := app.AccountKeeper.NewAccountWithAddress(ctx, addr1)
+	app.AccountKeeper.SetAccount(ctx, acc1)
+	s.Require().NoError(testutil.FundAccount(app.BankKeeper, ctx, addr1, balances))
+	store := ctx.KVStore(app.GetKey(types.StoreKey))
+
+	execFilterPaginate := func(store sdk.KVStore, pageReq *query.PageRequest, appCodec codec.Codec) (balances sdk.Coins, res *query.PageResponse, err error) {
+		balancesStore := prefix.NewStore(store, types.BalancesPrefix)
+		accountStore := prefix.NewStore(balancesStore, address.MustLengthPrefix(addr1))
+
+		var balResult sdk.Coins
+		res, err = query.FilteredPaginate(accountStore, pageReq, func(key []byte, value []byte, accumulate bool) (bool, error) {
+			var amount sdk.Int
+			err := amount.Unmarshal(value)
+			if err != nil {
+				return false, err
+			}
+
+			// filter odd amounts
+			if amount.Int64()%2 == 1 {
+				if accumulate {
+					balResult = append(balResult, sdk.NewCoin(string(key), amount))
+				}
+
+				return true, nil
+			}
+
+			return false, nil
+		})
+
+		return balResult, res, err
+	}
+
+	s.T().Log("verify next key of offset query")
+	pageReq := &query.PageRequest{Key: nil, Limit: 1, CountTotal: true}
+	balances, res, err := execFilterPaginate(store, pageReq, appCodec)
+	s.Require().NoError(err)
+	s.Require().NotNil(res)
+	s.Require().Equal(1, len(balances))
+	s.Require().Equal(balances[0].Amount.Int64(), int64(1))
+	s.Require().Equal(uint64(5), res.Total)
+	s.Require().NotNil(res.NextKey)
+
+	pageReq = &query.PageRequest{Key: res.NextKey, Limit: 1}
+	balances, res, err = execFilterPaginate(store, pageReq, appCodec)
+	s.Require().NoError(err)
+	s.Require().NotNil(res)
+	s.Require().Equal(1, len(balances))
+	s.Require().Equal(balances[0].Amount.Int64(), int64(3))
+	s.Require().NotNil(res.NextKey)
+}