Check image style exists for call out box

[andybroomfield]

Fix #124

If the image style large_21_9 isn't present, use the full url of the image.

[ekes]

Couple of questions:

• where is this paragraph style used?
• why could the image derivative type not exist?
• can it better be made configurable to a style that then does exist (and gets a dependency)?

[andybroomfield]

The call out box is used by subsites.
example: https://www.brighton-hove.gov.uk/madeira-terrace-restoration
BHCC are in the process of rationlising our image and media styles, as there are quite a lot and these are mostly used in support of the theme, and our image styles are different.
Currently we are leaving the styles in place until we are sure we can delete them . When we did delete them this issue came up.

Ideally this should be configurable, and we don't seem to encounter other issues as the other image and media styles are in config and are only an issue on initial install. Given this renderes as a background image, either a background image field formatter or loading the set image style from the media display would be the better way forward.

This PR is just to solve the initial bug though, so I'd like to move forward with it (Impact should be none form those who keep the image style around). For now we can then use our own theme preproccess hook to put the correct style in.

[finnlewis]

@ekes will take a look at this with respect to config for image styles

[ekes]

localgovdrupal/localgov_core#162 (comment) oof

I say get this in to stop breaking stuff and start a wider discussion on localgov_core/localgov_media

[finnlewis]

Agreed. Looks good to me too!

[andybroomfield]

Thanks all, yes, lets look at image styles seperatly.