r300: Don't crash in radeonUpdatePageFlipping when !radeon->glCtx->DrawBuffer.

This feels like a kludge, maybe there's a better solution.

diff --git a/src/mesa/drivers/dri/r300/radeon_lock.c b/src/mesa/drivers/dri/r300/radeon_lock.c
index 84181e2..0d0d9ab 100644 (file)
--- a/src/mesa/drivers/dri/r300/radeon_lock.c
+++ b/src/mesa/drivers/dri/r300/radeon_lock.c
@@ -60,7 +60,9 @@ void radeonUpdatePageFlipping(radeonContextPtr radeon)
            r300UpdateDrawBuffer(radeon->glCtx);
         }
 
-       use_back = (radeon->glCtx->DrawBuffer->_ColorDrawBufferMask[0] == BUFFER_BIT_BACK_LEFT);
+       use_back = radeon->glCtx->DrawBuffer ?
+               (radeon->glCtx->DrawBuffer->_ColorDrawBufferMask[0] ==
+                BUFFER_BIT_BACK_LEFT) : 1;
        use_back ^= (radeon->sarea->pfCurrentPage == 1);
 
        if (use_back) {