fix height on resize

fix height on resize

it already was in the comment but i forgot it:

some browsers need an even size,
so we do Floor(x/2)*2

but if we have an uneven height, we get a window
that is a pixel too small, resulting in a scrollbar

so we have to add 1 first (like with the width)
Floor((x+1)/2)*2

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>