RPC reports `stackHeight` of `null` for instructions at the base of the stack

[steveluscher]

Problem

Instructions that are declared in the transaction message should have a stackHeight of 1 but the RPC does not fill this property in, instead returning null

$ curl http://localhost:8899 -s -X   POST -H "Content-Type: application/json" -d ' 
  {
    "jsonrpc": "2.0",
    "id": 1,
    "method": "getTransaction",
    "params": [
      "3q8BdBE1deSudJA9DVKhh8zCXaLBgrfEVTo1GhNAUXhx3AYhCocUfXN8LQ1ME5B8VDBMqaf7GJY28kGdEpkjoU2G",
      "json"
    ]
  }
' | jq
{
  "jsonrpc": "2.0",
  "result": {
    "blockTime": 1744228013,
    "meta": {
      "computeUnitsConsumed": 2100,
      "err": null,
      "fee": 10000,
      "innerInstructions": [],
      "loadedAddresses": {
        "readonly": [],
        "writable": []
      },
      "logMessages": [
        "Program Vote111111111111111111111111111111111111111 invoke [1]",
        "Program Vote111111111111111111111111111111111111111 success"
      ],
      "postBalances": [
        499976100000,
        1000000000000000,
        1
      ],
      "postTokenBalances": [],
      "preBalances": [
        499976110000,
        1000000000000000,
        1
      ],
      "preTokenBalances": [],
      "rewards": [],
      "status": {
        "Ok": null
      }
    },
    "slot": 4785,
    "transaction": {
      "message": {
        "accountKeys": [
          "3jSivXpqhL8YXyEjSMWFsFpUpLRieycw8fXEaevG6yUh",
          "EcBrbtLfWfNa2jT3G6No3BBAwofXfHx5RW9nogs38Xmm",
          "Vote111111111111111111111111111111111111111"
        ],
        "header": {
          "numReadonlySignedAccounts": 0,
          "numReadonlyUnsignedAccounts": 1,
          "numRequiredSignatures": 2
        },
        "instructions": [
          {
            "accounts": [
              1,
              1
            ],
            "data": "67MGn8FGRGypi4prk7T3GCmTDPg6enaN6bgmY6iyA5uvS3zkAt2hf5v7w5f77Xo9NGnKoZG4A9sUU75uTXTf3bbHEMnX1E5gFC574UbRWkCEWCVsgNKyV671VGvB4yVHN3poupGcbshHS4JSsd6ne55ob1qbEhgKccqRbVpSEUk74eHNnkZcmQPSmBQnAyHyhMDG42Abcs",
            "programIdIndex": 2,
            "stackHeight": null
          }
        ],
        "recentBlockhash": "9HjALndAZq7HNDySMdse6cuAVnL8QZqa1PUmYHTkSZY5"
      },
      "signatures": [
        "3q8BdBE1deSudJA9DVKhh8zCXaLBgrfEVTo1GhNAUXhx3AYhCocUfXN8LQ1ME5B8VDBMqaf7GJY28kGdEpkjoU2G",
        "eRAn41FDYhwzytPQoKTPwy6aozZq38GD9RmXWaxMNAFdJz1EiuTYJgQzhrJNriaZxCm1ryFbF1f78JsWRQVxMcE"
      ]
    }
  },
  "id": 1
}

Proposed Solution

#5730.