NoMethodError: undefined method `new_pos' for nil:NilClass

https://sentry.gitlab.net/gitlab/gitlabcom/issues/2676648/?referrer=gitlab_plugin

NoMethodError: undefined method `new_pos' for nil:NilClass
  gitlab/github_import/representation/diff_note.rb:66:in `line_code'
    .diff_line_code(file_path, diff_line.new_pos, diff_line.old_pos)
  gitlab/github_import/importer/diff_note_importer.rb:34:in `execute'
    line_code: note.line_code,
  gitlab/github_import/object_importer.rb:37:in `import'
    importer_class.new(object, project, client).execute
  gitlab/github_import/rescheduling_methods.rb:31:in `try_import'
    import(*args)
  gitlab/github_import/rescheduling_methods.rb:19:in `perform'
    if try_import(project, client, hash)
...
(86 additional frame(s) were not displayed)

undefined method `new_pos' for nil:NilClass