Show alert box when a list / table is empty

If a lists / tables is empty, we should show a bootstrap "alert" box ("primary" variant) that informs that no items were found.

We don't currently do that in most places, but it would be more informative if we did this in all applicable places.

It _might_ be possible to handle this centrally in the `PagingControl`.

Start by locating the PagingControl and the places that render lists or tables, then inspect how empty results are currently handled. Done means all applicable empty lists and tables show a Bootstrap primary alert informing users that no items were found.

Written by the indexing model from the issue text.