securityReportFinding GraphQL query responds with error instead of null when pipeline has no findings

Summary

The securityReportFinding GraphQL query responds with error instead of null when pipeline has no findings. This happens because the FindingsFinder responds with nil and not an empty array. This needs to be handled in the FindingResolver properly.

Steps to reproduce

Make this GraphQL call, it responds with an error

query pipelineFindings {
  project(fullPath: "gitlab-examples/security/security-reports") {
    pipeline(sha: "33d6a1dc8d5083f1f67a907eac1d1972c2797feb") {
      startedAt
      status
      securityReportFinding(uuid: "testuuid") {
        uuid
        description
        reportType
      }
    }
  }
}

Example Project

What is the current bug behavior?

What is the expected correct behavior?

Relevant logs and/or screenshots

Output of checks

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of:
`sudo gitlab-rake gitlab:env:info`)

(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Possible fixes

Fix the FindingResolver to handle a nil response properly.