fix get graph

```
12:20:19 web.1     | TypeError - no implicit conversion of Symbol into Integer:
12:20:19 web.1     |    /home/seo.naotoshi/gitrepos/focuslight/lib/focuslight/web.rb:501:in `[]'
12:20:19 web.1     |    /home/seo.naotoshi/gitrepos/focuslight/lib/focuslight/web.rb:501:in `block in <class:Web>'
```

It should be correctly `stash[:graph]` rather than `hash[:graph]`