Fix the segmentation fault causing by NULL buffer object

Add if checking for dst_obj_surface->bo is NULL in
i965_proc_picture_fast function.

https://bugs.freedesktop.org/show_bug.cgi?id=92811

Signed-off-by: Lim Siew Hoon <siew.hoon.lim@intel.com>
Reviewed-by: Zhao Yakui <yakui.zhao@intel.com>

src/i965_post_processing.c

@@ -5722,6 +5722,9 @@ i965_proc_picture_fast(VADriverContextP ctx,
     if (!dst_obj_surface)
         return VA_STATUS_ERROR_INVALID_SURFACE;
 
+    if (!dst_obj_surface->bo)
+        return VA_STATUS_ERROR_UNIMPLEMENTED;
+
     if (dst_obj_surface->fourcc &&
         dst_obj_surface->fourcc != src_obj_surface->fourcc)
         pp_ops |= PP_OP_CHANGE_FORMAT;