There are two cases where this can happen if I visit http://localhost:8888/w/index.php/Special:Gather/by/Jdlrobson/70 where this is an empty collection.

1. Where the user is looking at a collection they do not own. e.g. Jdlrobson is not me This message makes no sense there.
2. When I visit my own collection e.g. Jdlrobson is me

Currently I see "Create a collection by clicking on the star icon while reading a JonWiki page."
in 1) this message doesn't help me fix that collection. "This is an empty collection" would be more informative. In 2) we should tell them to click edit.

"This is an empty collection."
If the collection belongs you below this you see:
"Add pages to the collection by clicking the edit button."