SproutCMS

Attempts to convert a link specification into a URL

This differs in behaviour to `Lnk::url` as it will return null if the spec is
empty, but *not* malformed; it still throws an InvalidArgumentException in that case.
It will also return null if a RowMissingException is thrown by the link spec instance
during processing.

Helpful when you wish to avoid breaking pages when someone deletes the linked record, e.g. a blog post,
without updating the corresponding link(s).