Error 500 when viewing a diff
https://sentry.gitlap.com/gitlab/gitlabcom/issues/41608/
NoMethodError: undefined method `new' for nil:NilClass
lib/gitlab/diff/file.rb:213:in `simple_viewer'
@simple_viewer ||= simple_viewer_class.new(self)
lib/gitlab/metrics/instrumentation.rb:156:in `block in simple_viewer'
trans.method_call_for(#{label.to_sym.inspect}).measure { super }
lib/gitlab/metrics/method_call.rb:23:in `measure'
retval = yield
lib/gitlab/metrics/instrumentation.rb:156:in `simple_viewer'
trans.method_call_for(#{label.to_sym.inspect}).measure { super }
app/views/projects/diffs/_content.html.haml:2:in `_app_views_projects_diffs__content_html_haml___3759556550658918483_70065597748160'
= render 'projects/diffs/viewer', viewer: diff_file.rich_viewer || diff_file.simple_viewer
...
(185 additional frame(s) were not displayed)
ActionView::Template::Error: undefined method `new' for nil:NilClass
ActionView::Template::Error: undefined method `new' for nil:NilClass