Consider changing assetId: 0x0000... of call receipt returned from graphql

[LuizAsFight]

Context

if you execute this query

query {
  transaction(id:"0xb3db00fb8261984407c7b308e926d4a928fa401eaf1c89c848a1733333128181") {
    status {
      __typename
      ... on SuccessStatus {
        receipts {
          __typename
          assetId
          amount
        }
      }
    }
  }

this contract call had no assets sent to it, therefore the assetId is returned as 0x0000....

Suggestion

Return assetId: null in this situation. I think it represents better that call didn't have an asset
Also as the baseAssetId of a network can be 0x0000... too, leads to confusion like "it represents the asset or null?"