jit.gl.sketch perfect corners when gllinewidth == 10

Hi all

This should be a quick one. I can't seem to get this simple one.
as the title indicates, I would for this framequad to have perfectly closed
corners when the gllinewidth is @ max (which seems to be 10)

Basically I seem to need to have the top/bottom OR Left/Right lines draw a little longer.

Here is the patch.
Thanks in advance for any help on this :-)

phil