only print link if it has a value

[markconroy]

Closes #866

What does this change?

1. Adds an if clause to only print the link field if it has a value
2. Remove the space from below the body of the call out
3. Add the space to the link field instead, so it's only available if there is an actual link

Call out - no link:

Call out - with link:

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Thanks to Big Blue Door for sponsoring my time to work on this.

[tonypaulbarker]

Looks good to me. Before these changes we get an empty button styled link with no link in it that looks broken. After changes looks neat.