Fix NoMethodError in dependency list page

What does this MR do and why?

Fixes the NoMethodError when accessing dependency list page for projects that has both dependency scanner and license scanner configured and the dependency scanner injects an invalid ancestor id.

See context: #415104 (closed)

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Before	After

How to set up and validate locally

Steps to reproduce

1. Create a new project with the following files:

.gitlab-ci.yml

dependency_scanning:
  script:
    - echo "test failing dependencies"
  artifacts:
    reports:
      dependency_scanning: gl-dependency-scanning-report.json

license_scanning:
  script:
    - echo "test failing dependencies"
  artifacts:
    reports:
      license_scanning: gl-license-scanning-report.json

gl-dependency-scanning-report.json

{
  "version": "15.0.0",
  "scan": {
    "analyzer": {
      "id": "gemnasium",
      "name": "Gemnasium",
      "url": "https://gitlab.com/gitlab-org/security-products/analyzers/gemnasium",
      "vendor": {
        "name": "GitLab"
      },
      "version": "4.0.2"
    },
    "scanner": {
      "id": "gemnasium",
      "name": "Gemnasium",
      "url": "https://gitlab.com/gitlab-org/security-products/analyzers/gemnasium",
      "vendor": {
        "name": "GitLab"
      },
      "version": "4.0.2"
    },
    "type": "dependency_scanning",
    "start_time": "2023-06-08T14:46:48",
    "end_time": "2023-06-08T14:46:53",
    "status": "success"
  },
  "dependency_files": [
    {
      "path": "BoloServices.JobFramework.Workflow.Activities/packages.lock.json",
      "package_manager": "nuget",
      "dependencies": [
        {
          "iid": 13,
          "dependency_path": [
            {
              "iid": 52
            },
            {
              "iid": 67
            },
            {
              "iid": 11
            }
          ],
          "package": {
            "name": "Microsoft.AspNetCore.Http"
          },
          "version": "2.1.1"
        },
        {
          "iid": 11,
          "package": {
            "name": "NLog.Web.AspNetCore"
          },
          "version": "4.9.0"
        },
        {
          "iid": 67,
          "package": {
            "name": "RSA.seahorse.Logging"
          },
          "version": "1.0.16"
        }
      ]
    }
  ],
  "vulnerabilities": [
    {
      "id": "853e5bd2f40053a75ff373dcf1a4862db71cf621c08dbf253c5562c5ac75bb7f",
      "name": "Cookie parsing failure",
      "description": "A security feature bypass vulnerability exists in the way Microsoft ASP.NET Core parses encoded cookie names. The ASP.NET Core cookie parser decodes entire cookie strings which could allow a malicious attacker to set a second cookie with the name being percent encoded. The security update addresses the vulnerability by fixing the way the ASP.NET Core cookie parser handles encoded names., aka 'Microsoft ASP.NET Core Security Feature Bypass Vulnerability'.",
      "cve": "",
      "severity": "High",
      "solution": "Upgrade to version 2.1.22 or above.",
      "location": {
        "file": "BoloServices.JobFramework.Workflow.Activities/packages.lock.json",
        "dependency": {
          "iid": 13,
          "package": {
            "name": "Microsoft.AspNetCore.Http"
          },
          "version": "2.1.1"
        }
      },
      "identifiers": [
        {
          "type": "gemnasium",
          "name": "Gemnasium-744de9f2-7edb-4e53-976c-d20777c420f8",
          "value": "744de9f2-7edb-4e53-976c-d20777c420f8",
          "url": "https://gitlab.com/gitlab-org/security-products/gemnasium-db/-/blob/master/nuget/Microsoft.AspNetCore.Http/CVE-2020-1045.yml"
        }
      ],
      "links": [
        {
          "url": "https://github.com/advisories/GHSA-hxrm-9w7p-39cc"
        }
      ],
      "details": {
        "introduced_by_package": {
          "type": "text",
          "name": "Introduced by Package",
          "value": "BoloServices.jobframework:"
        },
        "shortest_path": {
          "type": "list",
          "name": "Shortest Path",
          "items": [
            {
              "type": "text",
              "value": "BoloServices.jobframework:"
            }
          ]
        },
        "vulnerable_package": {
          "type": "text",
          "name": "Vulnerable Package",
          "value": "Microsoft.AspNetCore.Http:2.1.1"
        }
      }
    }
  ]
}

gl-license-scanning-report.json

{
    "version": "2.1",
    "licenses": [
      {
        "id": "Apache-2.0",
        "name": "Apache License 2.0",
        "url": "https://opensource.org/licenses/Apache-2.0"
      }
    ],
    "dependencies": [
      {
        "name": "AWS.Logger.AspNetCore",
        "version": "2.1.1",
        "package_manager": "nuget",
        "path": "Bolo.JobEngine.sln",
        "licenses": [
          "https://aws.amazon.com/apache-2-0/"
        ]
      },
      {
        "name": "AWS.Logger.Core",
        "version": "1.5.1",
        "package_manager": "nuget",
        "path": "Bolo.JobEngine.sln",
        "licenses": [
          "https://aws.amazon.com/apache-2-0/"
        ]
      }
    ]
  }

2. Trigger a new pipeline on the default branch
3. Ping http://<HOST>/<PROJECT_FULL_PATH>/-/dependencies.json

The following error will be triggered:

NoMethodError at /root/test-dependency/-/dependencies.json
undefined method `fetch' for nil:NilClass
                  next ancestor unless ancestor.fetch(:iid, false) # `block (2 levels) in augment_ancestors!': undefined method `fetch' for nil:NilClass 

4. With the fix, we should not see the NoMethodError.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #414559 (closed)