UX: Sometimes the footer would show up while refreshing a list route (PR #14666)

This happens because the state of canLoadMore is not cleared as the refresh occurs, which is enough to make the page think a footer should be displayed.

No tests here because it’s tricky to test refreshing and none of our existing acceptance tests seem to.


@eviltrout I believe this overrides a computed property and causes deprecation warnings

Should it set model.more_topics_url to null instead?