NoMethodError: Projects::BlameController#show

Problem

Sentry error: https://new-sentry.gitlab.net/organizations/gitlab/issues/954568/

NoMethodError: undefined method `html_safe' for nil:NilClass

        current_group[:lines] << (highlight ? highlighted_lines[i].html_safe : line)
                                                                  ^^^^^^^^^^
Did you mean?  html_safe?
  from lib/gitlab/blame.rb:32:in `block in groups'
  from lib/gitlab/git/blame.rb:21:in `block in each'
  from lib/gitlab/git/blame.rb:20:in `each'
  from lib/gitlab/git/blame.rb:20:in `each'
  from lib/gitlab/blame.rb:23:in `groups'
  from app/presenters/gitlab/blame_presenter.rb:36:in `groups'
  from app/presenters/gitlab/blame_presenter.rb:55:in `precalculate_data_by_commit!'
  from app/presenters/gitlab/blame_presenter.rb:28:in `initialize'
  from lib/gitlab/view/presenter/factory.rb:13:in `new'
  from lib/gitlab/view/presenter/factory.rb:13:in `fabricate!'