Error 500 creating a merge request: NoMethodError: undefined method `downcase' for nil:NilClass
https://sentry.gitlap.com/gitlab/gitlabcom/issues/121199/
NoMethodError: undefined method `downcase' for nil:NilClass
app/services/merge_requests/build_service.rb:165:in `assign_title_from_issue'
branch_title = source_branch.downcase.remove(issue_iid.downcase).titleize.humanize
lib/gitlab/metrics/instrumentation.rb:159:in `block in assign_title_from_issue'
.measure { super }
lib/gitlab/metrics/method_call.rb:36:in `measure'
retval = yield
lib/gitlab/metrics/instrumentation.rb:159:in `assign_title_from_issue'
.measure { super }
app/services/merge_requests/build_service.rb:129:in `assign_title_and_description'
assign_title_from_issue if target_project.issues_enabled? || target_project.external_issue_tracker
...
(127 additional frame(s) were not displayed)
NoMethodError: undefined method `downcase' for nil:NilClass