Section 6.1.3 (Text Strings) of the SMBIOS specification states: If a string field references no string, a null (0) is placed in that string field. Change smbios_add_string() to do that. Change-Id: I9c28cb89dcfe2c8ef2366c23ee6203e15b7c2513 Signed-off-by: Ben Gardner <gardner.ben@gmail.com> Reviewed-on: https://review.coreboot.org/12697 Tested-by: build bot (Jenkins) Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>