fix: check space and proposal exist

[wa0x6e]

in vp operation, check that proposal and space exist, and return meaningful error otherwise.

With this test query

query Vp{
		vp(
			space: "rocketposfsdfol-dao.eth",
      proposal: "asas",
			voter: "0x0000000000000000000000000000000000000000",
		) {
			vp
		}
	}
	

Before fix, it returns

{
  "errors": [
    {
      "message": "Cannot read properties of undefined (reading 'network')",
      "locations": [
        {
          "line": 2,
          "column": 3
        }
      ],
      "path": [
        "vp"
      ]
    }
  ],
  "data": {
    "vp": null
  }
}

After fix, it returns

{
  "errors": [
    {
      "message": "space not found",
      "locations": [
        {
          "line": 2,
          "column": 3
        }
      ],
      "path": [
        "vp"
      ]
    }
  ],
  "data": {
    "vp": null
  }
}

[ChaituVR]

utAck