Improve error handling with pages shortcode

[harrybigspring]

When using the pages shortcode, if you don't provide page IDs then you will get a PHP error. The shortcode needs to handle cases where there is no page ids.

[juliotaylor]

I propose that in production mode, it does not display an error at all to
save it looking shit on live sites. On dev mode we can display an elegnt
error.

[jrgmartin]

Agreed!

[juliotaylor]

@jrgmartin what's the plan here?

[jrgmartin]

It's relatively simple to build in some logic based around the the production and dev mode.

[juliotaylor]

is this something we need to move over to M3?