Deleting an issue breaks Security Dashboard

Summary

When an issue is created via the security dashboard for a vulnerability, if that issue is later deleted, it breaks the group-level security dashboard. This is true even if the issue is already resolved and not even visible in the vulnerability list.

Steps to reproduce

Create an issue from a security vulnerability. Delete the issue. Run the security dashboard for the group level above that project.

Example Project

This happened on a self-managed instance. I tried to repro on GitLab.com, but do not have delete ability for issues in my own project group on GitLab.com.

What is the current bug behavior?

Group security dashboard no longer works

What is the expected correct behavior?

Group security dashboard should still work

Relevant logs and/or screenshots

NoMethodError (undefined method `iid' for nil:NilClass):
  
ee/app/serializers/vulnerabilities/feedback_entity.rb:21:in `block in <class:FeedbackEntity>'
app/serializers/base_serializer.rb:16:in `represent'
app/serializers/concerns/with_pagination.rb:19:in `represent'
ee/app/serializers/vulnerabilities/occurrence_serializer.rb:17:in `represent'
ee/app/controllers/groups/security/vulnerabilities_controller.rb:19:in `block (2 levels) in index'
ee/app/controllers/groups/security/vulnerabilities_controller.rb:14:in `index'
lib/gitlab/i18n.rb:55:in `with_locale'
lib/gitlab/i18n.rb:61:in `with_user_locale'
app/controllers/application_controller.rb:434:in `set_locale'
lib/gitlab/middleware/multipart.rb:103:in `call'
lib/gitlab/request_profiler/middleware.rb:16:in `call'
ee/lib/gitlab/jira/middleware.rb:17:in `call'
lib/gitlab/middleware/go.rb:20:in `call'
lib/gitlab/etag_caching/middleware.rb:13:in `call'
lib/gitlab/middleware/correlation_id.rb:16:in `block in call'
lib/gitlab/correlation_id.rb:15:in `use_id'
lib/gitlab/middleware/correlation_id.rb:15:in `call'
lib/gitlab/middleware/read_only/controller.rb:42:in `call'
lib/gitlab/middleware/read_only.rb:18:in `call'
lib/gitlab/middleware/basic_health_check.rb:25:in `call'
lib/gitlab/request_context.rb:26:in `call'
lib/gitlab/metrics/requests_rack_middleware.rb:29:in `call'
lib/gitlab/middleware/release_env.rb:13:in `call'

ogs cannot be copied off closed network

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)
Latest Omnibus was used, output cannot be shared due to being on a closed network.

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)
Latest Omnibus was used, output cannot be shared due to being on a closed network.
(we will only investigate if the tests are passing)

Possible fixes

(If you can, link to the line of code that might be responsible for the problem)