Simplify code involving gtk_tree_list_row_get_item()
It's return value used to nullable, which has forced us to cope with that.
(It turns out there was a better approach: listening to GtkTreeListRow::notify:item
. Anyway, it's not necessary anymore.)
Now it's no longer NULL. So, we always get the item in the ::undbind
signal handlers, as expected.
Therefore, there is some code cleanup to do (with a GTK dependency bump).