Attempt to redirect to wiki-page when page is nil

https://sentry.gitlab.net/gitlab/gitlabcom/issues/1658055/?referrer=gitlab_plugin

ActionController::UrlGenerationError: No route matches {:action=>"show", :controller=>"projects/wikis", :id=>nil, :namespace_id=>#<Namespace id: 5997929, name: "Mladen Knezic", path: "mladen.knezic", owner_id: 4567483, created_at: "2019-09-05 11:00:25", updated_at: "2019-09-05 11:00:25", type: nil, description: [FILTERED], avatar: nil, membership_lock: false, share_with_group_lock: false, visibility_level: 20, request_access_enabled: false, ldap_sync_status: "ready", ldap_sync_error: nil, ldap_sync_last_update_at: nil, ldap_sync_last_successful_update_at: nil, ldap_sync_last_sync_at: nil, lfs_enabled: nil, description_html: "", parent_id: nil, shared_runners_minutes_limit: nil, repository_size_limit: nil, require_two_factor_authentication: false, two_factor_grace_period: 48, cached_markdown_version: 1114115, project_creation_level: nil, runners_token: nil, file_template_project_id: nil, saml_discovery_token: nil, runners_token_encrypted: nil, custom_project_templates_group_id: nil, auto_devops_enabled: nil, extra_shared_runners_minutes_limit: nil, last_ci_minutes_notification_at: nil, last_ci_minutes_usage_notification_level: nil, subgroup_creation_level: 1, emails_disabled: nil, max_pages_size: nil, max_artifacts_size: nil, mentions_disabled: nil, default_branch_protection: nil, unlock_membership_to_ldap: nil, max_personal_access_token_lifetime: nil, push_rule_id: nil>, :project_id=>#<Project id:15470778 mladen.knezic/videobox>>}
  action_dispatch/journey/formatter.rb:57:in `generate'
    raise ActionController::UrlGenerationError, message
  action_dispatch/routing/route_set.rb:738:in `generate'
    @set.formatter.generate(named_route, options, recall, PARAMETERIZE)
  action_dispatch/routing/route_set.rb:769:in `generate'
    Generator.new(route_key, options, recall, self).generate
  action_dispatch/routing/route_set.rb:816:in `url_for'
    path, params = generate(route_name, path_options, recall)
  action_dispatch/routing/url_for.rb:180:in `full_url_for'
    _routes.url_for(merged_url_options, route_name)
...
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ActionController::UrlGenerationError: No route matches {:action=>"show", :controller=>"projects/wikis", :id=>nil, :namespace_id=>#<Namespace id: 5997929, name: "Mladen Knezic", path: "mladen.knezic", owner_id: 4567483, created_at: "2019-09-05 11:00:25", updated_at: "2019-09-05 11:00:25", type: nil, description: [FILTERED], avatar: nil, membership_lock: false, share_with_group_lock: false, visibility_level: 20, request_access_enabled: false, ldap_sync_status: "ready", ldap_sync_error: nil, ldap_sync_last_update_at: nil, ldap_sync_last_successful_update_at: nil, ldap_sync_last_sync_at: nil, lfs_enabled: nil, description_html: "", parent_id: nil, shared_runners_minutes_limit: nil, repository_size_limit: nil, require_two_factor_authentication: false, two_factor_grace_period: 48, cached_markdown_version: 1114115, project_creation_level: nil, runners_token: nil, file_template_project_id: nil, saml_discovery_token: nil, runners_token_encrypted: nil, custom_project_templates_group_id: nil, auto_devops_enabled: nil, extra_shared_runners_minutes_limit: nil, last_ci_minutes_notification_at: nil, last_ci_minutes_usage_notification_level: nil, subgroup_creation_level: 1, emails_disabled: nil, max_pages_size: nil, max_artifacts_size: nil, mentions_disabled: nil, default_branch_protection: nil, unlock_membership_to_ldap: nil, max_personal_access_token_lifetime: nil, push_rule_id: nil>, :project_id=>#<Project id:15470778 mladen.knezic/videobox>>}