Internal Error on deleted issue

Got next error with redmine_keyboard_shortcuts on deleted issue page

```
ActionView::Template::Error (undefined method `id' for nil:NilClass):
    4: <script type="text/javascript">
    5:   var ks_projects = <%= Project.visible.find(:all, :select => 'name, identifier', :order => 'lft').to_json.html_safe %>;
    6:   <% if (params[:controller] == 'issues' && params[:action] == 'show') then %>
    7:     var ks_issue_id = <%= @issue.id %>;
    8:   <% end %>
    9: </script>
```