In commit 905ac48bb we mentioned:
> Since we don't use `asset_path` to reference assets in the public
> folder, we can safely disable the `unknown_asset_fallback` option.
However, `asset_path` is used by the wicked_pdf gem when calling the
`wicked_pdf_stylesheet_link_tag` method. This method also checks the CSS
files, searching for `url()` calls and converting any relative URLs
referenced there to absolute URLs.
However, when compiling assets on production, our `application.css` file
contains the following line imported from Leaflet which says:
```
behavior: url(#default#VML);
```
When passing this URL to `asset_path` (which is something the wicked_pdf
gem does automatically), it doesn't find the URL, and so this call
crashes unless we enable then `unknown_asset_fallback` option.
Since the dashboard poster is a feature we might remove in the future,
we're avoiding changing a Rails global configuration just for this
feature. So, instead of enabling the `unknown_asset_fallback` option,
we're changing the `poster.pdf` view so it doesn't load all the CSS of
the application but only the CSS it needs.
Note we aren't adding a test case because this bug is only present on
production environments when assets have been precompiled.
