svga: move LIST_INITHEAD(dirty_buffers) earlier in svga_context_create()

Fixes a crash in svga_context_flush_buffers() if we use the 'draw' module
for AA lines (when the device doesn't support that feature).  We need to
initialize this list before we setup the swtnl pieces.

Found/fixed by Charmaine Lee.

Cc: "10.0" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>
1 file changed