improve error handling of substreams powered subgraphs

[shiyasmohd]

Fixes #5749

Deployed a SPS to studio with error - QmRxqwbpjKxmAQkXVgAwS65xvtAyyoVSpxd1J554AxYFN6

curl --location 'https://api.thegraph.com/index-node/graphql' \
--header 'Content-Type: application/json' \
--data '{"query":"{\n        indexingStatuses(subgraphs: [\"QmRxqwbpjKxmAQkXVgAwS65xvtAyyoVSpxd1J554AxYFN6\"]){\n            subgraph\n            synced\n            health\n            fatalError {\n                message\n                handler\n                deterministic\n            }\n            nonFatalErrors{\n                message\n                block{number}\n            }\n        }\n    }","variables":{}}' | jq .

This request returns subgraph is still healthy and doesn't add any error to fatal Errors field

{
  "data": {
    "indexingStatuses": [
      {
        "subgraph": "QmRxqwbpjKxmAQkXVgAwS65xvtAyyoVSpxd1J554AxYFN6",
        "synced": false,
        "health": "healthy",
        "fatalError": null,
        "nonFatalErrors": []
      }
    ]
  }
}

This PR fixes this issue.

Index node api response when locally running this branch and deploy the SPS with error

{
    "data": {
        "indexingStatuses": [
            {
                "subgraph": "QmRxqwbpjKxmAQkXVgAwS65xvtAyyoVSpxd1J554AxYFN6",
                "synced": false,
                "health": "failed",
                "fatalError": {
                    "message": "error while executing at wasm backtrace:\t    0: 0x43f2 - <unknown>!src/mappings/handleTriggers: Entity Token[0x4200000000000000000000000000000000000006]: missing value for non-nullable field `totalSupply`: Entity Token[0x4200000000000000000000000000000000000006]: missing value for non-nullable field `totalSupply`",
                    "handler": null,
                    "deterministic": false
                },
                "nonFatalErrors": []
            }
        ]
    }
}