[rpc] fix: catch ErrAddressNotPresent old block

The validator list is not per block, while the information being sought
is. Therefore, do not return error if validator address is not present
in state.

Fixes #4202

core/state/statedb.go

@@ -808,7 +808,7 @@ func (db *DB) Commit(deleteEmptyObjects bool) (root common.Hash, err error) {
 }
 
 var (
-	errAddressNotPresent = errors.New("address not present in state")
+	ErrAddressNotPresent = errors.New("address not present in state")
 )
 
 // ValidatorWrapper retrieves the existing validator in the cache, if sendOriginal
@@ -834,7 +834,7 @@ func (db *DB) ValidatorWrapper(
 
 	by := db.GetCode(addr)
 	if len(by) == 0 {
-		return nil, errAddressNotPresent
+		return nil, ErrAddressNotPresent
 	}
 	val := stk.ValidatorWrapper{}
 	if err := rlp.DecodeBytes(by, &val); err != nil {
@@ -897,7 +897,7 @@ func (db *DB) UpdateValidatorWrapperWithRevert(
 	// a copy of the existing store can be used for revert
 	// since we are replacing the existing with the new anyway
 	prev, err := db.ValidatorWrapper(addr, true, false)
-	if err != nil && err != errAddressNotPresent {
+	if err != nil && err != ErrAddressNotPresent {
 		return err
 	}
 	if err := db.UpdateValidatorWrapper(addr, val); err != nil {

core/state/statedb_test.go

@@ -1019,7 +1019,7 @@ func verifyValidatorWrapperRevert(
 ) {
 	state.RevertToSnapshot(snapshot)
 	loadedWrapper, err := state.ValidatorWrapper(wrapperAddress, true, false)
-	if err != nil && !(err == errAddressNotPresent && allowErrAddressNotPresent) {
+	if err != nil && !(err == ErrAddressNotPresent && allowErrAddressNotPresent) {
 		t.Fatalf("Could not load wrapper %v\n", err)
 	}
 	if expectedWrapper != nil {

rpc/staking.go

@@ -11,6 +11,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/harmony-one/harmony/core/state"
 	"github.com/harmony-one/harmony/eth/rpc"
 	"github.com/harmony-one/harmony/hmy"
 	internal_common "github.com/harmony-one/harmony/internal/common"
@@ -366,7 +367,14 @@ func (s *PublicStakingService) getAllValidatorInformation(
 	for i := start; i < start+validatorsNum; i++ {
 		validatorInfo, err := s.hmy.GetValidatorInformation(addresses[i], blk)
 		if err != nil {
-			return nil, err
+			if errors.Cause(err) != state.ErrAddressNotPresent {
+				return nil, err
+			} else {
+				// GetAllValidatorAddresses is as of current block
+				// but we are querying state as of prior block
+				// which means we can ignore ErrAddressNotPresent
+				continue
+			}
 		}
 		// Response output is the same for all versions
 		validators = append(validators, validatorInfo)