FIX: show selected topic with above-topic-list-item

[Gravitonic]

In a topic item list, the row currently selected by the j/k keyboard shortcuts is indicated by a style applied to the td:first-child of selected rows, but the "above-topic-list-item" plugin outlet allows for inserting elements as the first child of those rows. If the inserted element is not a <tr> element, then there's no element matching the CSS selector and thus no way to tell what row is currently selected to navigate from.

For example, the Clickable Topic plugin inserts a hidden <div> in the "above-topic-list-item" plugin outlet which means there's no visual indication of what item is selected.

[pmusaraj]

Thanks @Gravitonic, this makes sense!