Fix VulerabilityType.identifiers field when vulnerability.finding returns nil

The vulnerability report page is failing for the following filtering combinations; https://gitlab.com/gitlab-org/gitlab/-/security/vulnerability_report/?sortBy=detected&sortDesc=false&activity=ALL&state=ALL

{
  vulnerability(id: "gid://gitlab/Vulnerability/1") {
    id
    project {
      name
    }
    identifiers {
      name
    }
  } 
}

This throws an error:

{
  "errors": [
    {
      "graphQLErrors": [
        {
          "message": "Cannot return null for non-nullable field Vulnerability.identifiers",
          "locations": [
            {
              "line": 7,
              "column": 5
            }
          ],
          "path": [
            "vulnerability",
            "identifiers"
          ]
        }
      ],
      "clientErrors": [],
      "networkError": null,
      "message": "Cannot return null for non-nullable field Vulnerability.identifiers",
      "stack": "Error\n    at new t (https://gitlab.com/assets/webpack/main.734e0d82.chunk.js:1:68160)\n    at https://gitlab.com/assets/webpack/main.734e0d82.chunk.js:1:314525\n    at Object.next (https://gitlab.com/assets/webpack/main.734e0d82.chunk.js:69:111978)\n    at y (https://gitlab.com/assets/webpack/main.734e0d82.chunk.js:69:109874)\n    at k (https://gitlab.com/assets/webpack/main.734e0d82.chunk.js:69:110380)\n    at e.next (https://gitlab.com/assets/webpack/main.734e0d82.chunk.js:69:110913)\n    at https://gitlab.com/assets/webpack/main.734e0d82.chunk.js:63:116748\n    at Array.forEach (<anonymous>)\n    at i (https://gitlab.com/assets/webpack/main.734e0d82.chunk.js:63:116716)\n    at Object.next (https://gitlab.com/assets/webpack/main.734e0d82.chunk.js:1:292848)"
    }
  ]
}

Though we are using in few places finding but only identifiers field is non-null:

https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/app/graphql/types/vulnerability_type.rb

Possible fixes:

To fix this specific scenario:

• We can use vulnerability_finding instead of finding in the identifiers method so that it returns finding incase vulnerability_id is nil in finding

or,

• Make this field null: true so that we do not throws error when finding is nil.

Follow up:

As a follow up, we should fix the data or association.