[PyGObject] TreeView: Empty integer field or right aligned string

[<c buhtz posteo jp>]

X-Post: https://stackoverflow.com/q/50194505/4865723

I want to have in a Gtk.TreeView

    - empty cells in a "int row" of a TreeView
    - or (as a workaround) a right aligned "string row"

There is a screenshot and example code in the StackOverflow question
linked in the first line of this post.

The problem is

    - When I give 'None' to a 'int row' a '0' is displayed. I would
      expect an empty cell. I want that cell to be
      absolute empty.

    - A workaround is to use strings instead of int and just display the
      numbers as strings doing str(int).
      But then the content of each cell is left aligned by default.
      I tried to modify that. But this also has no effect.

I attached the full example.