cubicweb-relationwidget #5491694 items are deselected on addition of a new item [open]

I'm currently the latest public cset: abe5b4a629ea

When clicking on items in the central table, the items are correctly appended to the selected list (in the lower part), but previously selected items in the center are de-selected.

prioritynormal
typebug
done in<not specified>
closed by<not specified>