applets/kicker: fix direct activation for other cols
Kicker allows you to directly activate the first hit when searching by pressing Return from the search field; the entry is also highlighted to inform the user. However, this always activates the first runner model, not the first visible column's runner model. So if the first column is generally Applications, but there are no hits there and only in Settings, it will just not work without indication.
Instead of always using the first model, iterate through them until we find one that has content, like we already do for e.g. arrow key nav.
Test plan:
- Open kicker, search for "shortcuts", press Return
- (without) doesn't work (with) works