Error when resizing the UI window

[sub26nico]

When resizing UI window, wolf-spectrum doesn't act correctly:
a black (empty) band appears on the window anf if I reduce the window size,
the spectrum only show the top of the spectrum window, it's not resizing the entire window.
Maybe related to #31
I made a video : https://exode.me/videos/watch/23dd18a3-05e1-456b-afad-00b16907c8e4