applets/kicker: show placeholder on empty search result
Kickoff shows a simple placeholder message when a completed search returns no matches. Kicker, however, just shows empty space. This is a bit unclear, and as there is no indicator whether the search is still running, it's also unclear whether there are actually no matches or the file runner just needs a little more time.
Instead, show a placeholder very similar to the one for kickoff. It'll only be shown once the search is actually complete.
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