i965_drv_video: Added check of obj_surface->bo field inside i965_media_h264_surface_state()

i965_drv_video/i965_media_h264.c

@@ -297,6 +297,8 @@ i965_media_h264_surface_state(VADriverContextP ctx,
     dri_bo *bo;
     uint32_t write_domain, read_domain;
 
+    assert(obj_surface->bo);
+
     bo = dri_bo_alloc(i965->intel.bufmgr,
                       "surface state", 
                       sizeof(struct i965_surface_state), 32);