Empty row not showing in Table

Hello, Vaadin-afficionados!

I’m facing a weird Table-issue:

To visually separate entries on a (later printed) pdf i insert empty rows into a collection of records,
which is represented by a table.
The “empty” records are there, but the table simply doesn’t show up the empty lines (please see the attached screenshot)

Any ideas?

best regards from styria/austria
Wolfgang
13091.jpg