Subgraph returning null for some addresses

Question

I have deployed a version of the open-zeppelin-subgraph (https://github.com/OpenZeppelin/openzeppelin-subgraphs) and I am tracking ERC20, ERC721 and ERC1155 tokens.

I am using this query:

    {
        account(id: "${walletAddress}") {
            ERC20balances {
                id
                value
            }
            ERC721tokens {
                id
                identifier
            }
            ERC1155balances {
                token {
                    id
                    identifier
                }
                valueExact
            }
        }
    }

The problem I have is that instead of getting empty arrays for wallets that does not have a balance of the tokens I am tracking, I am getting this:

{
  "data": {
    "account": null
  }
}

Why is this happening only for some addresses? I think this is the format I should get no matter what addresses I use:

{
  "data": {
    "account": {
      "ERC20balances": [],
      "ERC721tokens": [],
      "ERC1155balances": []
    }
  }
}

Answer 1

open-zeppelin-subgraph uses this function every time an account takes part in a transaction or event you are tracking in your subgraph:

export function fetchAccount(address: Address): Account {
    let account = new Account(address)
    account.save()
    return account
}

By "taking part" I mean being a sender or a receiver of a token or being a proposer or a voter. This will vary depending on the type of contracts you are tracking.

So, if the account you are looking for has never taken part in any transaction or event of the ones you are indexing, that account will appear as null because it has never been saved to the database as an account entity.