fix

core/blockchain_reader.go

@@ -374,7 +374,7 @@ func (bc *BlockChain) StateAt(root common.Hash) (*state.StateDB, error) {
 	// Instead of that, it will be more useful to return an error to indicate
 	// the state is not available.
 	if stateDb.NoTrie() && stateDb.GetSnap() == nil {
-		return nil, errors.New("state is not available")
+		return stateDb, errors.New("state is not available")
 	}
 
 	return stateDb, err