Mesa (gallium-mesa-7.4): mesa: only call update_buffer when it's available

[Alan Hourihane]

Module: Mesa
Branch: gallium-mesa-7.4
Commit: d71910c1567d73ba112ff4b6f44be6572ad51da9
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=d71910c1567d73ba112ff4b6f44be6572ad51da9

Author: Alan Hourihane <alanh at vmware.com>
Date:   Fri Feb 20 14:40:08 2009 +0000

mesa: only call update_buffer when it's available

---

 src/mesa/state_tracker/st_cb_viewport.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/src/mesa/state_tracker/st_cb_viewport.c b/src/mesa/state_tracker/st_cb_viewport.c
index 6adf316..7b17528 100644
--- a/src/mesa/state_tracker/st_cb_viewport.c
+++ b/src/mesa/state_tracker/st_cb_viewport.c
@@ -40,7 +40,7 @@ static void st_viewport(GLcontext * ctx, GLint x, GLint y,
 {
    struct st_context *st = ctx->st;
 
-   if (st->pipe->winsys)
+   if (st->pipe->winsys && st->pipe->winsys->update_buffer)
       st->pipe->winsys->update_buffer( st->pipe->winsys,
                                        st->pipe->priv );
 }