500 error while viewing merge request

Summary

I'm encountering a 500 error while attempting to load the following merge request:

gitlab-org/security-products/analyzers/klar!26 (merged)

Steps to reproduce

Open link to gitlab-org/security-products/analyzers/klar!26 (merged)

What is the current bug behavior?

500 is returned

What is the expected correct behavior?

Merge request should open

Relevant logs and/or screenshots

Sentry Issue: GITLABCOM-D8F0

NoMethodError: undefined method `latest_closed_at' for nil:NilClass
  blocking_merge_request_entity.rb:32:in `block in <class:BlockingMergeRequestEntity>'
    blocking_mr.metrics.latest_closed_at
  active_support/json/encoding.rb:22:in `encode'
    Encoding.json_encoder.new(options).encode(value)
  active_support/core_ext/object/json.rb:42:in `to_json'
    ActiveSupport::JSON.encode(self, options)
  delegate.rb:83:in `method_missing'
    target.__send__(m, *args, &block)
  issuables_helper.rb:88:in `serialize_issuable'
    .to_json
...
(245 additional frame(s) were not displayed)

ActionView::Template::Error: undefined method `latest_closed_at' for nil:NilClass

ActionView::Template::Error: undefined method `latest_closed_at' for nil:NilClass

Output of checks

This bug happens on GitLab.com