GtkListBox placeholder or filter can break rounded borders on last row selection
Adding a placeholder, or filtering some result in a GtkListBox breaks the ":last-child" css rules making selected last item bottom borders rounded (see below)
Without placeholder :
![Without placeholder](data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==)
With placeholder:
![With placeholder](data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==)