st/nine: Ignore window size if error

st/nine: Ignore window size if error

Check GetWindowInfo and ignore the computed sizes
if there is an error.

Fixes a regression caused by earlier commit when
using old wine gallium nine patches.

Should also address a crash at window destruction.

Related issues:
 https://github.com/iXit/Mesa-3D/issues/331
 https://github.com/iXit/Mesa-3D/issues/332

Cc: mesa-stable@lists.freedesktop.org
Fixes: 2318ca68bbe ("st/nine: Handle window resize when a presentation
buffer is used")

Signed-off-by: Axel Davy <davyaxel0@gmail.com>